Coming into this thread late, but as noted, 2.5″ pipes are a waste of money for a 215. I wanted to maintain ground clearance on my 62 wagon. A single 2.5″ pipe in the stock location has MORE cross sectional area than two 1.75″ pipes. It should have even less flow resistance since there’s less surface area in a single pipe of the same cross sectional area vs. twin pipes. so there’s less boundary layer drag in the pipe.
I used a pre-bent Walker cat-back pipe for a fourth-gen Camaro. I had to make some minor mods to the part over the rear axle and I had to build a front section from mandrel bends to mate to the stock Y-pipe. Not ideal but it works. I used a Magnaflow single inlet/dual outlet muffler (also for a Camaro) mounted in the stock location, with a pair of S-bend pipes exiting behind the rear wheels.