Headers usually give the most HP. You also need good flowing heads (are they ported?) and exhaust system (what size are you running?). LBM's will breath better than the Logs. It's hard to say how many HP more the headers will give over the LBM's without knowing the other varialbles. But in general, you could see 30-40 hp more with headers over LBM's and the same for LBM's over logs. Unless you're numbers matching (which doesnt look the case), I wouldnt be putting logs on a new rebuild. At a minimum LBM's.
