Headers VS 340 manifolds

Before you spend alot on 340 manifolds here is some interesting information. http://www.moparmusclemagazine.com/techarticles/155_0307_mopar_crate_engine_exhaust/index.html Check out this test by mopar muscle on a 300 HP crate 360. Less then 10 hp gain going from 318 to 340 manifolds, and less then 20 going from 318 manifolds to TTI's. If your car is a mild build and a cruser I would just use the 360 pieces that match the ports and save some money. If your planning on a hot engine then of course these numbers would probably spread out more I think.