2.5 inch or 3 inch

My bud built his own set for his SBC powered 71 Maverick running S/G. He raced it in some Quick races, too. Best of in the mid 7's on nitrous! His exhaust was worrkin! LOL
What you are really payin for with those guys is the quality and the lack of compromise on the headers construction.
They seem to knoe their stuff about the physics of exhaust flow...how much do ya gain with their stuff? I don't know...what do the record holders run? They specifically mentioned S and SS I think....