I had them on my 35 chevy 454 BBC. I found that they were way to restrictive. I had 2 1/2" pipe to the rear ( no muffers) and then the Supertraps. I tried them with with up to 13 baffles. Cut a hloe in the end cap. Made my own baffles. Now I just use the housing as tail pipes. Flowmaster 70 series mufflers. Much better.