Produced by Chevrolet from 1973 to 1991, the “square body” K5 Blazer is one of the most iconic SUVs designs in automotive history. Over its eighteen years of production the second-generation K5 saw numerous design updates and technological upgrades, and by the late 80s it was a modernized machine that offered electronic fuel injection, an overdrive transmission, and a 350ci small-block making a respectable 210 horsepower and 300 pound-feet of torque.

This – combined with the timeless charm of a two-door, body-on-frame sport utility vehicle with a removable top and a design that had no regard for aerodynamic drag – helped to convince the current owner of this 1988 K5 to get it back on the road after an extended hibernation.

Even with the high beams on, the old headlights in this Blazer just weren’t cutting it.

The initial work focused on rehabilitating the big stuff like the engine, transmission, transfer case, brakes, suspension, and so on. Once the truck was more or less roadworthy, attention turned to the smaller, less urgent issues. But while getting the radio working again is a problem that can be set aside for a while, others proved to be a bit more troublesome. The headlights, for instance, were so dim that it made the truck virtually undrivable at night.

Eager to address this shortcoming once and do it right, LEDs immediately considered. But there was a sticking point: The owner wanted to retain the K5’s period-correct aesthetic, and many of the factory replacement LEDs that are currently on the market mess with the classic sealed-beam look. The solution? Holley RetroBright LED headlights.

How easy is it to upgrade the headlights in my classic vehicle?

Modern Tech, Classic Look

Developed with Morimoto – an industry leader in high-end automotive LED lighting – and designed to plug into the original harness with no alteration of the factory wiring, Holley RetroBright LED headlights offer period-correct appearance and direct fitment while delivering more than twice the lighting output of a halogen.

These LEDs also draw less current than halogens (a bonus for a three-decade-old electrical system like this one) and they generate less heat as well. The LED cartridges are also designed to be replaceable when the time comes for servicing.

While some applications are plug and play, others may require an adapter in order to match the wiring on the factory harness. This kit also allowed us to adapt the LFRB120’s three-pong configuration to the high beams’ two-prong plug on this K5.

The no-glare beam pattern created by Holley’s RetroBright LED headlights meets or exceeds SAE and DOT requirements, and for this application they’re available in modern white (5700K color temperature), classic white (3000K color temperature), or with yellow lenses for a bit of European flair. We chose classic white for this install because we didn’t want to change or update the look – we just wanted more of that original warm hue.

A Simple Installation

The simplicity of older Chevy full-size trucks makes them a breeze to wrench on when compared to the complexity and tight confines of modern vehicles, and this headlight installation was certainly no exception to the rule.

After disconnecting the battery, we popped the hood and removed the two T10 Torx screws that fasten the top of each headlight bezel to the upper section of the grille, along with the two T10 torx screws on the bottom of each bezel that secures them to the lower part of the grille. The headlights themselves are attached to the metal headlight buckets with four screws – two at the top of the headlight and two at the bottom.

The additional screws at the top and outside edge of each light are there to adjust the alignment of the headlights. These alignment screws are held in with plastic clips that can deteriorate and break over time, so you may want to consider stocking up on some new ones ahead of time and replace them while you’ve got everything off. This requires the additional step of re-aligning all the headlights after you’re done, of course, so if the clips aren’t broken it’s entirely optional.

After unscrewing the headlight from the bucket and removing the metal headlight surround, the headlight can be freed from the truck by simply disconnecting it from the harness. For this installation we used four of the LFRB120 lights, which can be used for both the low beam lights and the high beam lights below them. However, Holley also now offers the LFRB121 light, which has a two-prong connector that’s designed specifically for the high beam wiring harness, so that’s also an option for those who’d prefer to avoid using an adapter to connect those lights up.

What modifications do I need to make to convert my classic vehicle's headlights to LED?

Included in each box along with the lights themselves are two connector housings and three color-coded wires that allow you to create harness adapters for different models and year ranges. The LFRB120 light has a three-pong connector, so in some applications no adapter is required when hooking up to the factory low beam harness – it’s literally plug-and-play. However, for this 1988 K5 we had to put together the adapters to match the wiring layout of this truck’s harness; the details on how to put the adapter together for various applications can be found here. Although it’s a bit of extra fiddling, the adapter went together without any drama and created a secure connection, as the wiring clicks into place when it’s properly seated in the connector housings.

Since we used the three-pong LFRB120 lights for the high beams we also put together two-prong adapters for those lights – the details of that assembly are also provided in the instructions linked above. Once everything hooked up (and we replaced a few broken headlight alignment adjusters that we discovered along the way), we tested the lights to make sure everything was copasetic. After that it was just a matter of reversing the disassembly process to get everything buttoned back up.

These LEDs offer six times the longevity of halogen sealed beams, and the cartridges are designed to be replaceable for easy serviceability.

To say that the RetroBrights were an improvement over the beat down lights that we took out would be massive understatement. Although the new LEDs look virtually identical to the original sealed beam units when they’re turned off, they’ve dramatically increased nighttime visibility without being obnoxious or out of step with truck’s aesthetic. The owner tells us that driving the Blazer after dark is an entirely different experience now, and he plans to take it out more often as a result.

It might be easy to dismiss sub-par lighting as a minor issue, but if it’s keeping your ride sitting in the driveway instead of out on the road, that seems like a pretty big deal to us. If this situation reminds you of one of your projects, Holley RetroBright LED headlights might be just what you need in order to bring that whip back to daily driver status.