There is an old R&T article by Tony Hogg about his narrow hipped street car (original 2X4 427 SO) His had the undercar exhaust that was in poor condition when he bought it and he talks about have a muffler shop set him up with glass packs and the exit was in front of the rear wheels.
I'd really like to do this set up too, but I worry more ground clearance than performance, since I neither need, nor will have 500hp (might as well live to see 40
)
Mike