318 build #2 "cost minded" for the '74 Duster

There is another dyno test between manifolds and found that best combo was one 340 and one 5.9l forget which ones but here's non magnum manifold and header shoot out

Installing Exhaust Headers Into 300hp Crate Engine - Mopar Muscle Magazine
Headers didn't seem to make much of a difference on this combo over manifolds.