I am running a '72 AMC 360 out of a J-20 Pickup. There is a set of exhausts on Ebay right now....side pipes for fenderwell headers, with the cats welded to the collectors, and mufflers welded directly to the cats, with side pipes directly after. Like samjluck said, a tight fit, I am sure! Can be done, tho. Do a search, I ran across them yesterday, sorry, don't remember the number.
With stock manifolds, your exhaust will run inside the frame rails and "thru" your skidplate area. My problem with my in-frame headers/exhaust, which is similar to the problems you may have, is that they rub my brake lines, get in the way of clutch adjustment, header has to be removed to change the starter, exhaust constantly rubs the tranny or skidplate somehow, rubs my rear shocks, etc.
I love rear exhaust sound, but it is a royal PITA to run the exhaust so it doesn't rub anything. My best success with rear exhaust was with my last setup....a built 258 with dual exhaust headers, then I spent $400 to have a custom exhaust shop build my system. Best $400 spent, took the guy 8 hours to do it (all day), and came out beautiful.
With the V8, a different story.....I really think side pipes with fenderells is the best option all around.