9. The 1969 Ford Boss 429 Was Built Around The Engine
Literally, the engine was produced first and then the car was built to fit around it. The engine was created, to start, from the Ford 385 engine. It used four bolt mains, a forged steel crank and connecting rods. The engine was too wide to fit the current Mustang body, thus the Boss 9 was created. NASCAR required that any engine be outfitted in production and sold to 500 customers before it could race professionally. It is estimated that just over 1300 Ford Bos 429s were created.