you have to switch or you wont be able to bolt it to the motor without an adapter plate .i dont like them .if you have an early 8 bolt case and pump you must find an 8 bolt chevy or install 2 2004r parking pawl cup plugs in the extra holes in the pump or install a 6 bolt pump.if you find a late 6 bolt , 7 ball case make sure you dont install the extra check ball and you drill out the low reverse cup plug in the case to at least .200 or youll have a crappy 1/2 manual upshift because of delayed reverse band disengagement.