I can tell you that it isn't easy to quiet down a stroked windsor.
My 85 with a 575hp 418 in it has had 2 exhaust systems in it.
#1. 1 3/4 headers, to a pair of dynomax bullets, thru and X pipe, thru a pair of 2 chamber flowmasters and then tail pipes.
#2. same headers, straight piped to a pair of ultraflows, and then tailpipes. Still all 3"
The ultraflow setup is definitely quieter. I would have liked to try it with the bullets and X in front of it to see how quiet it would be....but there is no way someone wouldn't know it was packing some serious power.
My advice would be to run the ultraflows, keep it 2.5", and run an X pipe to try to swallow up the sound.
1984 GT, 363 -RHS215 heads & Super Vic intake by MCRP, FTI cam, Carbureted, Glide, 4.30's, pump gas, street legal, N/A
Bests:1.35 60' / 6.21 /9.76 and 138.8 mph.
Thanks MCRP, UCC, FTI, Sepanek, Braswell, Racecraft, and Team Z