When I ran a very mild 383 in my old Dart I did have headers on it. But the 383 was a stock bottom end and I mean stock as it was not even bored as it was stock bore. I had 452 heads I milled to get a true 9.5 comp and I did some mild pocket porting on the heads. All the internals were stock other then the MP .484 cam and I had it on a 104 ICL. I used stock rockers and pushrods and had a Comp single spring on the valves. Everything else was bolt on's like the RPM intake and 750 Holley DP. It had 3.91's and weighed 3560 with him in it. It ran 12.30's @ 110 with a 12.31 best. I was impressed with how nice that mild 383 ran. Ron