NOS is nice, but I dont think I spent much more than that on the entire pypes settup for my 77.
Theres as guy in NY I think (sorry for the lack of info but I am sure its out there) that makes a correct exhaust. Guys that want 'concours' quality use this kind of thing. I have heard they are quite pricey as well. I have read about him on the PY site. Someone there may have his name and number if you want exact.