Magnum exhaust manifolds
Dunno if ALL the magnum manifolds are the same but I believe they used the same ones on 318 and 360 full size pickup trucks. They are supposed to flow much better than the LA mannies. I say use them if you have them. Headers are ALWAYS a pain in the a$$ and look like crap a year or two. Put the Magnum manifolds on and forget about it for a few decades.
C