383 Exhaust Manifiolds vs. Headers

Manifolds are not a terrible way to go. They are in many cases, a better flowing design then other brands cast iron options. Bear in mind the FAST (factory appearing stock tire) class of racing that go rediculiously fast through stock manifolds. I would take the time to clean up the ports, and collector as best I could and then run a good mandrel bent exhaust system to be as efficient as possible.