If you're running the stock 273 exhaust manifolds on the 318, just use the Commando/Charger 273 exhaust system. No mods needed, they fit easily, sound great, and can handle the 318 displacement just fine. The bottleneck is the manifolds, not the exhaust system. Oh, and I've seen many early A's with dual exhaust and without the transmission crossmember mod. They just dip down a bit to clear, and usually end up with a dent in the pipe right there. If you're going to go with headers, the old Spitfire, Doug's, and TTI make them to fit to one degree or another. My Spitfires fit nice with a 360, but, they aren't available anymore except under a different name. (Did Layson's buy them out?) With headers, yeah, mod the trans mount and go full duals with an X crossover if it's going to be driven on the street.
