I have an art morrison frame, but made my own cutouts, they were not offering it when I bought mine, lil behind
I drilled (I think the size is correct, it was 12 years ago) 3.5" holes and welded in some 3/16" wall pipe. Then used some silicon sheet in between the pipe and my 3" exhaust tubes. It was a tight fit. And to be honest, I dont know if it helped with sound. My car is too noisy. But the thing with car noise is you have to tackle every point of noise and whittle it down. It will keep the metal on metal noise down. And the silicon sheet will hold up to the heat. JR