I had a complete three inch sytem on my old Duster, that car had coil overs on it so the exhaust shop ran the 3 inch tailpipes under and around the rear end housing and mounted the three inch by 14 inch long oval Magnaflows between the rear end and the rear bumper outside 1/4 panel and the rear subframes behind the rear end. It had a stock Gas tank also. I'm puttng a 1966 Coronet Deluxe two door sedan together right now,440 4 speed car now I bought the Summit three inch B body exhaust system for it but I haven't taken that system out of the shipping box yet . I did buy a set of 3 inch Ultra flows for the car and plan on mounting them back behind the rear end like my Duster had, I had the rear leaf springs move into the rear subframes and moved the rear end forward two inches I'm using a new stock gas tank also so it might be lots of fun routing the exhaust back there