318 vs 340 exhaust manifolds

Too bad they didn't use a 3" collector on the headers or have everything stub on cast iron to a 2.5" tube. May have moved things a little. I'd bet that the tti headers would have worked really well on that engine.

Funny that the 2 pass side early 340 manifolds kicked the snot out of the original matched set. The drivers side exhaust manifolds are turrrrrrible! LOL There's not that much difference in cast iron IMO, to justify spending the money on early 340 manifolds. For the difference, I can buy a 75hp juice unit and kill the 340 manifold runner. :)

For the OP, run what you got and save some money would be my approach, unless you want to boast about having 340 manifolds...