Need Exhaust Pictures PLEASE!!!
Best bet is to take it to a good local muffler shop (NOT Midas!!) and have the guys there look it over. I work part time a muffler shop locally and we get these types of problems all the time. Except for tti exhaust systems, most aftermarket sets don't fit up very well. I have a 1970 Duster 340 with factory duals from Summit and the fit is awful. Not the fault of Summit but the guy who put them on weld EVERYTHING together. No, I haven't had time to fix it either. Anyway, with your springs mounted inboard and using 2 1/2" diameter exhausts pipes, it might just be a matter of rebending the "U" part over the rear axle. If the shop can't do that, they can custom bend something that will fit your situation. Sorry, don't have any pictures of the exhaust system on mine but I doubt that would help anyway. Let me know if this helps.