5.9MAGNUM EXH MANIFOLDS

There's not a big difference in power its up to you. Manifold and header shoot out, magnum are similar to 340 manifold performance, there another shoot out somewhere shows the best pair is one 340 and one magnum, forget which ones.

Installing Exhaust Headers Into 300hp Crate Engine - Mopar Muscle Magazine
I can’t see the full article. It seems like a good one. Just like everyone on here has mentioned long tube headers for early A cars are stupid money. I found the idea of running the magnum exhaust interesting and coincides with what a gentleman locally mentioned to me off handedly. I was going to buy the Doug’s Headers but if it’s a small difference in power it’s worth looking into.