There easily changed. The ones I have had taper. I have cut a few 2.5" Flow Master and made them 3" sized inlets/outlets..
About a 10 minute fix with a Mig. The mufflers them selves are the same.

[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]