Everywhere I look, people want big dollars for 1968-70 340 exhaust manifolds. I see great set of headers that would work great and usually a third of the cost, but people would rather spend their dough on those manifolds.

My question is, if there was a hp diffrence in 340, 318 and 1971-later 340 manifolds, what is that diffrence and is it practical hp number to support a decently build small block?