I'm looking for the same thing as you with my '70 318 Duster. My plan is to go with an X-pipe system from Pypes Exhaust, then just have a local muffler shop fab up some headpipes. I know those systems w/o mufflers run about $360; adding in mufflers (nice ones from Classic Chambered) and labor, total comes to maybe $500, which I think isn't too bad for an X-pipe system with high-quality mufflers.