The flanges should be the same size so it should bolt up fine...but you might want to consider taking a dremel to the smaller flange to make a smoother flow into the larger pipe. In my experience if you dont' do that you will get some raspiness.rufeo wrote:i just got a 5zigen rocket exhaust that has 3 in piping for my 91. i wasnt sure if that would bolt right up to the cat or would there need to be modification. i dont wanna hear about if 3 in is too big. this is what i have so plz keep answers to my questions. not trying to be d**k but ive read all the posts about it.