I've used Mac products on 2 mustangs and have never had a problem. I ran shorties with an offroad H back in the mid '90s on my '93 for several years, and I had some long tubes on my current mustang for over a year with a prochamber. I switched to Kooks when I wanted to go to a 1 7/8" setup, but I am still running the prochamber.
My buddy had a 1 5/8" shorties, 2.5" offroad H, and 2.5" mac mufflers and it sounded awesome.