I'll be the tie-breaker; headers are best left to those who are after the last bit of power from their engines. They are generally a high maintenance item,though some people just have better success than others with them.
You'll find the old rams-horn manifolds to be tough and reliable,and you won't lose enough power vs. headers to be worth quibbling about. (If you should happen across a set from an old 1960-1966 C-60 or bigger with a smallblock,they often have bigger outlets,to use bigger pipes,and make slightly bigger power.) Of course,they were really big with the big racers,so finding them could be a big undertaking.
Speed
