If you go with a Flowmaster, depending on which one you choose and who is doing the job, change the outlet to the top of the muffler rather than the end of it, kind of like the old Volvo mufflers. This way the pipe can go back right to the axle. If I recall I had a 5 X 9 Flowmaster on my turbo Monti, Do not remember how long but I generally use the longest I can. I angled the inlet and brought the rear up high so it had a straight shot over the axle. Had to add a heat shield over the rear of it. Nice thing about a turbo is the truck only has the cat on it now, still is quiet.