I am currently in the process of building my 91 Z/28 5.7L. Right now I have just headers on for any kind of exhaust. They are Hooker 2460HKR headers. I do want to put the Magnaflow 23479 Direct Fit Dual Cat back on (A.I.R. system is disconnected) going into a Flowmaster American Thunder Force II 2.5" cat back. I know I need a reducer from the header to the cats, since they are 2.25" and the headers are 3". The cats have a 2 bolt flange, and unfortunatly the headers have a 3 bolt flange. Can the flanges be cut off and then the new cats be welded to the reducers. The only size reducers they offer are from a 3" to a 2.125" or from a 3" to a 2.5". Is .125" or .25" to much of a gap to weld. I do want to keep the essential stock setup because of me being in the Army, I might be stationed somewhere where there is emission testing and all. So I really do not want to completley eliminate the cats, nor do I really want to modify a Y-pipe to accept a cat. Any thoughts would be greatly appreciated.