Fits big and small block Chevy engines. It requires that you use this in conjuction with part # FPT flexplate (139 tooth ten pitch). It is mandatory that the two ten pitch components be used together. the starter and flexplate combination will install exactly like a normal 12 pitch (std Chevy) combination but will provide a deeper and stronger gear set. Chevy offset for 139 tooth 10 pitch flexplate Super Duty drive