Was the dyno run through mufflers, or open? On the street, the exhaust is bottled up so that would likely negate some gain. I don't mind installing the shorties if they will provide a notable gain, but is it worth the effort and need to go back to the exhaust shop to have them join the existing exhaust to the new headers? That is my question. Also, I am running the 1970 340 manifolds if that makes any difference.
