Which company built the original Shelby Mustang models for Ford?

Shelby American built the original Shelby Mustang models for Ford. Carroll Shelby’s California company transformed ordinary Mustangs into high-performance GT350 and GT500 variants, beginning with the 1965 model year.

Ford asked Shelby to develop a Mustang suitable for competition after the standard car’s sporting credentials proved limited. Shelby American added performance equipment including revised intake and exhaust systems, stronger brakes, suspension changes, and distinctive bodywork. The GT350 quickly became a successful SCCA B-Production racer.

Production expanded in 1966 with options such as an automatic transmission and the Hertz GT350-H rental cars. In 1967, Shelby added the big-block GT500, powered by Ford’s 428-cubic-inch V8. These cars were assembled at Shelby’s Los Angeles facility from partially completed Ford Mustangs.

A common mix-up is assuming Shelby American built every first-generation Shelby Mustang. Ford took greater control after 1967, and production moved to Michigan for 1968; Ford had functional control of design and production by the 1969 model year. Thus, Shelby American is the canonical answer for the original Shelby-built Ford Mustangs.