I considered true duals and chose not to go that way due to the loss of ground clearance. The 61-63 cars have a floor pan with an offset tunnel to allow the single exhaust pipe to fit next to the driveshaft. I found that the Walker 2.5″ cat-back pipe for a fourth-gen F-body fits almost exactly – I had to make some minor tweaks on the bend over the axle. I fabricated a front section that mated to the stock Y-pipe. If an Olds 455 breaths fine with two 2.5″ pipes, a 215 will have more than enough airflow with a single 2.5″ pipe. I also wanted a muffler that fit in the stock location. I finally found a Magnaflow for a third-gen F-body that had a single 2.5″ inlet and two 2.5″ outlets that fit behind the rear axle. Sounds awesome, especially over 3000 RPM.