Heads

They should be either a "516" casting, or an earlier version thereof. If they are stock, they will have a smaller exhaust valve than your '72 heads, 1.60" Vs. 1.74". Stock flow on the older heads is worse than the '72 castings. The early heads are a closed chamber design, and will gain you a little compression. All in all, unless you do some work to the early heads, you are better off with what you have on your '72.