The Boss 429 was a For Mustang variant offered in 1969 and 1970. It is arguably one of the rarest and most valued muscle cars to date . In total there were 1,358 Boss 429's made. The origin of the Boss 429 comes about as a result of NASCAR. Ford was seeking to develop a motor that could compete with the Hemi motor from Chrysler in NASCAR's Sprint Cup Series (then known as "Grand National Division"). NASCAR's homologation rules required that at least 500 cars be fitted with this motor and sold to the general public. After much consideration, it was decided by Ford that the Mustang would be the car that would house this new engine. The Boss 429 engine was derrived from the Ford 385 engine. The Mustang's body however was not wide enough to encompass the massive Boss 429 engine and as a result, Ford hired Kar Kraft out of Dearborn, MI to modify existing 428 Cobra Jet Mach 1 Mustangs to properly fit the new Boss 429 engine. Kar Kraft made extensive modifications to the Mustang, including widening the shock towers and extended out the inner fenders to allow this massive engine to fit. In addition, a hole was cut in the hood and a manual controlled hood scoop was added to these cars. These cars were rated at 375hp and 450ft·lb of torque.