Introduced when the automotive industry was still deep in the throes of the Malaise Era, the 1979 Ford Mustang was one of the first signs of light at the other end of the high-performance tunnel. Serving as the successor to the much-maligned, Pinto-based Mustang II, the third-generation pony car rode on the Blue Oval’s recently-unveiled Fox platform, a “one-size-fits-all” rear-wheel drive architecture that was designed to accommodate everything from two-door sportscar to five-door station wagons with powertrains ranging from inline four-cylinders to small-block V8s.
Although engine performance was still clawing its way out of the darkness at the time – the ’79 Mustang GT’s 5.0-liter V8 made all of 139 horsepower – Ford’s focus on simplicity and lightness in the development of the Fox platform resulted in a V8-powered production car that weighed about 2,600 pounds. That’s just a few hundred pounds more than the diminutive Mazda Miata that would make its debut a decade later, and nearly three-quarters of a ton lighter than today’s Mustang GT.
Thanks to ongoing improvements on the OEM side as well as the strong aftermarket support that sprouted up in its wake, the Fox-body Mustang went on to become one of the performance icons of ‘80s and ‘90s. Today it remains the platform of choice for many drag racers, and that robust aftermarket ecosystem has also enabled autocrossers and road racers to turn these cars into formidable corner carving machines as well. In many ways, it has evolved into the ultimate hot rodding template: A basic lightweight rear-wheel drive platform with V8 and manual transmission compatibility right out of the box that allows enthusiasts to build whatever their mind’s eye can see – even if that vision is simply a fun, low-budget runabout for cruise nights.
Folks tend to think of the Fox-body platform’s run ending when production of the third-gen Mustang concluded in 1993, but in reality, the architecture that underpinned its SN-95 and New Edge successors is actually an updated iteration of the Fox platform. With the conclusion of New Edge Mustang production in 2004, the Fox platform was finally put out to pasture after 26 years of service, making it the second-longest run of a vehicle architecture in Ford’s history.
As a result, there are still tons of well-sorted, low-mileage examples to be had of both the boxy, ‘80s-style variety as well as the more sophisticated and powerful four-generation cars, many of which can still be found for well under $15,000. And as Holley Performance’s resident Fox-body guru Matt Lunsford points out, a growing number of enthusiasts are starting to take notice.
“Those characteristics offer a lot of advantages for high-performance builds, so clean ones are becoming a little harder to come by these days. But you also have to remember that even the most potent factory versions of that pushrod 5.0 made less than 250 horsepower, so a modern minivan would give them a run for their money. And things like structural rigidity weren’t really a big concern at those power levels. There’s a lot of room for improvement here, no matter which way you want to go with the build.”
Shop all of Holley's Fox Body Mustang performance parts here.
With that in mind, we’re taking a look at the upgrades that should be on the top of hit list for any Fox-body Mustang build.
Short-Throw Shifter – With the exception of some early iterations and a handful of SVT models in the 2000s, virtually all manually-shifted Fox-body V8 Mustangs were equipped a five-speed gearbox produced by Borg Warner or Tremec. While the presence of a third pedal significantly enhances up the fun factor in these cars, Lunsford tells us that the factory shifters left something to be desired.
“A short-throw shifter would be my first upgrade right out of the gate because it will really improve the driving experience without costing a ton of money. Those factory shifters just had a lot of slop, and it’s also pretty easy to miss the 2nd-to-3rd upshift. But a short-throw shifter like the Hurst Billet Short-Throw will give the car a noticeably more performance-oriented vibe while also addressing those issues.”
Compared to the factory units, the Hurst shifter offers much more precise action and reduces the shift throw by a whopping 30%. Meanwhile a strong centering spring more effectively guides the shifter into the gates, thereby reducing the likelihood of missed shifts.
“A lot of folks dig the old-school cue ball look, too,” he says. “But for those that want to keep things stealthy, you also have the option of adapting the factory shift arm and knob to the Hurst hardware for a more factory-style aesthetic.”
Cat-Back Exhaust – Whether your tastes gravitate toward understated performance or all-out mania, no Fox-body Mustang build is complete without a cat-back exhaust system. Not only do these kits provide a visual upgrade over the boring factory tailpipes, they allow you to tailor the engine soundtrack to your preference and pick up some power while doing so.
“A Fox-body Mustang with a chambered Flowmaster exhaust systems just an iconic combination,” Lunsford notes. “And because you can buy mufflers like the 40-Series separately, you can do dump-style system if you prefer to go that route rather than a setup with stainless tailpipes at the rear.”
Flowmaster’s American Thunder series kits offer the aggressive sound that has become synonymous with modified 5.0 Mustangs of the era, but the company also offers Force II and Flow FX kits as well as mellower 50-Series Delta Flow chambered mufflers for these cars too, in turn allowing builders to get an exhaust tone that fits their builds perfectly.
Rear-End Gearset – The vast majority of Fox-body-based Mustangs were equipped with 2.73, 3.08, or 3.27 rear end ratios from the factory. While these fuel economy-minded ratios make these cars mellow highway cruisers, they leave a lot on the table when it comes to performance. Switching to a more aggressive gearset will allow the engine to get into the meaty parts of its powerband quicker, which will in turn result in more rapid acceleration. It’s an upgrade that you’ll feel in the seat of your pants and see on your timeslips.
“This is the biggest bang-for-the-buck upgrade for a Fox-body Mustang,” Lunsford says. “Even a 3.55 kit will really wake these cars up, and if you’re got a manual car, that overdrive fifth gear allows you to go with something like a 3.73 or 4.10 ratio and still keep the RPMs pretty low on the highway – especially if it’s a Fox-body with a Modular V8, which has a wider RPM range than the pushrod 5.0.”
Subframe Connectors – As we noted earlier, structural rigidity wasn’t a particularly high priority during the development of the Fox-body chassis, and that lack of stiffness starts to become a liability when you add power and start throwing suspension upgrades into the mix.
“For me, this is the point where you should start looking at supporting mods; upgrades that will benefit the build as it continues to evolve,” Lunsford says. “And the first one that comes to mind for me is subframe connectors. This is my number one modification for these cars – any Fox-body gets subframe connectors if I touch it.”
By tying together the frame rails at the front and rear of the car, subframe connectors significantly enhance the chassis’ torsional stiffness, and this reduction in chassis flex allows the suspension to do its job more efficiently, which will improve both launch and cornering performance. Subframe connectors can also help prevent cracking in the rear torque box, a common issue with Fox-body Mustangs.
Upgraded Fuel Pump – While the Fox-body’s factory fuel pump can handle the demands of a stock example and maybe even a few bolt-ons, the story quickly starts to change if you take things any further.
“This is another key supporting mod,” says Lunsford. “At about 300 horsepower or so, the factory pump starts to run out of juice; it just can’t keep up with the fueling demands. And when that happens the engine can potentially start to run lean, which is an issue both in terms of performance and longevity.”
He points to Holley Performance’s range of fuel pump upgrades for Fox-body Mustangs, which include both external and in-tank modules, as a means to address the problem while opening the door to forced induction and other power adders.
“You might not feel the difference right after the install, but you’ll know that you’re going to have enough fuel to support the demand that you’ll have further down the road.” And considering the cost of the next upgrade in our list, you might arrive at those power levels sooner than you think.
Nitrous Kit – “A system like the NOS wet nitrous kit allows you to add 150 horsepower for about $800. There’s really no other way to get those kinds of power gains for that kind of money, and that’s why these systems continue to be so popular,” Lunsford says. “The factory internals of the pushrod 5.0 can handle it, but you’ll need that fuel pump upgrade to meet the increased fuel demand. Although this kit is universal, it was developed specifically with Fox-body Mustangs in mind. It’s designed to work with cars that still have the factory computer – since it’s a wet kit, you’re not relying on a computer to add fuel, so you don’t need to upgrade your injectors to make it work. The only other thing you need is that upgraded fuel pump.”
When you're upgrading your Fox Body Mustang to go fast don’t overlook stopping power. Baer Brakes’ 13-inch Classic Series front brake system offers an excellent balance of performance and style. This kit features Baer’s original two-piston, pad-guided caliper (PGC), finished in a bold red powder coat with a black logo. It's mounted to a 13-inch, one-piece rotor that’s slotted, drilled, and zinc plated for both function and durability. Designed specifically for 1979–1993 Fox Mustangs with 1994–2004 SN95 spindles and hubs, this system does not fit stock 79–93 spindles.
The package includes mounting brackets, stainless braided hoses, and all necessary hardware, and is compatible with most 17" or larger wheels. A crucial note for anyone setting up their braking system: this kit is optimized for vehicles running a 15/16" master cylinder and a proper pedal ratio. Manual brake setups can use a 7/8" master cylinder for easier pedal effort, but anything larger than 15/16" will demand excessive pedal input to achieve proper brake performance.
Stepping back to take the long view, Lunsford says that when going into a project like this, it’s important to keep in mind how the car is actually going to be used, as that will serve as a guide when selecting upgrades and other components.
“At the end of the day, the goal is to have fun and enjoy these things. There’s always that urge to get the wildest camshaft or the loudest exhaust, but people often don’t realize until after the fact that those decisions can impact the car’s usability. Unless you’re building a dedicated race car, you have to be measured about the parts you select for build because if you go overboard, it may become something that you don’t want to just jump in and use. If the goal is to drive it as much as possible, you have to keep that in mind and be wise about the choices that you make.”
