I have the 3.5" by 6" long schoenfelds on my 434 SBF. Running supercomp headers with 3.5" collector. I cut the 3 bolt flange off and used a straight band clamp to attach the schoenfeld to the headers. I notched the muffler and put a hole in the band clamp around the O2 sensor bung, so that helps keep it all together without getting loose and coming off the header. They toned it down a little, but not much. My class required mufflers. Just don't stick your fingers up inside the muffler LOL, those sharp edges in there will get ya.