Deciding on replacement intake (318, details in post)

Do you know what the cylinder heads flow? Mabe the tunnel ram was ported to match. The ram is going to flow more no matter how much porting you do to any single 4 barrel intake. Figure that a rpm airgap which is the popular manifold of choice, is not going to flow over 240 cfm with the best of porting. So going the single 4 barrel route you may be disappointed if your heads flow more and your new manifold is the new choking point in your combination.