Early 72 340, is this one of the de-tuned ones?

The factory manifolds are actually pretty good- but they're heavvvy. That said, clean it up good, plug the EGR port in the bottom of the plenum, an EGR blockoff plate, and you may as well block the heat crossovers too (you won't need it in NM), port match if you feel so inclined; and you'll have a solid, decent performing manifold.