I worked with my exhaust guy and took his recommendation on using Dynomax turbo mufflers, 2.5” diameter and an H pipe. He kept the center section easily removable for simple clutch service. He had to heat up and slightly bend the passenger side header collector inward just a bit to clear the floor pan. The JBA stainless tri-Y headers are nice and tight to the car… just a bit too tight for collector clearance on the passenger side. Being an early car with the hand cut valence and chopped-off GT aluminum trim, we used some stainless tips that fit nicely.
Hoping this setup sounds great and maximizes the engine improvements over stock. I do have the original cast iron manifolds, and intermediate pipes with correct resonators for returning it to factory original down the road.