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Flowmaster American Thunder Header-back Exhaust System

Fits 1964-1966 Mustang, 2.50-inch stainless steel system.

PART# 817273

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$870.00   Suggested Retail
$782.95   Your Price
Estimated shipping date: 12/11/2020
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Aggressive to moderate sound


This American Thunder® headers-back exhaust system is designed for all 1964-1966 Ford Mustang hardtop coupes with a V8 engine. The system features a free-flowing 2.50-inch mandrel-bent stainless steel H-pipe flowing into a pair of Super 44® Series mufflers for maximum power and that deep iconic sound. The 2.50-inch mandrel-bent stainless tailpipes tuck up high and are finished off with a pair of long 2.50-inch 304 stainless steel tips for that show car look. Includes all necessary parts, hardware and easy to follow instructions and is covered by our Lifetime Limited Warranty. Note: Does Not fit GT models or convertibles.


  • Includes Hangers and Hardware for an Easy Installation
  • Mandrel-bent 16-gauge Stainless Steel Tubing
  • Super 44 Series Performance Mufflers
  • Long Polished Stainless Steel Tips
  • Includes Built-in "H" Balance Pipe
  • Moderate Exterior Exhaust Tone
  • Lifetime Limited Warranty
  • Headers-back System


Emission Code3
Exhaust SeriesAmerican Thunder
Exit PositionDual Out Rear
Heat ShieldNo
Inlet Diameter (in)2.5
Material409 Stainless Steel
Muffler Part NumberKit Only
Muffler Quantity2
Muffler Series40 Series Delta Flow
Outlet Diameter (in)2.5
Product TypeExhaust System
Single DualDual
Sound LevelAggressive / Moderate
System TypeHeader-back
Tip Diameter (in)2.5
Tip Quantity2
Tubing Diameter (in)2.5
California Proposition 65 Chemical NameChromium (hexavalent compounds)
Nickel (Metallic)
California Proposition 65 RequiredYes
Part Number817273



This part is legal for sale and use on Uncontrolled (Non-Emissions Controlled) Vehicles and Racing Use Only Vehicles.

The following vehicles are considered Uncontrolled (Non-Emissions Controlled) Vehicles:

  • 1965 and older U.S. manufactured California Certified vehicles
  • 1967 and older U.S. manufactured Federally Certified vehicles
  • 1967 and older Foreign manufactured vehicle

The following vehicles are considered Racing Use Only Vehicles:

  • Racing Use Only Vehicles are vehicles that are used exclusively for competition and that are not registered and that may never be used on the street

WARNING: It is against the law to install this part on an Emissions Controlled Vehicle

The following vehicles are considered Emissions Controlled Vehicles:

  • 1966 and newer U.S. manufactured California Certified vehicles
  • 1968 and newer U.S. manufactured Federally Certified vehicles
  • 1968 and newer Foreign manufactured vehicle

Tech Resources

Does not fit GT or convertible models.


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        Some parts are not legal for use in California or other states with similar regulations.

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