I had a few custom longlifes on small bumpers, had an SS "replica"
on my early Mk2 with single 2.5" pipe exit and painted in back box
Also used Std 16v back box with custom unit up to down pipe, new oversize pipe cut and welded into std B box.
Big shiney exhausts on small bumpers tend to look wrong if not done
with care.

Up rated mounts are essential, seen so many Mk2s with the back box swinging around not good