Headers vs 360 manifolds for 318

In answer to the op's question, headers won't get you a bunch more power unless you build your combination around their performance potential. I had a stock 73 340 Challenger that I put Mickey Thompson try Y's on. I didn't change anything else on the combination. I had been running it on the strip and it actually went slower by .2 with the headers in the 1/8th than with the stock manifolds and factory dual exhaust.