I don't think there's a magic load for all M1A type rifles. You'll have to experiment with different loads in YOUR rifle and see what yields the best results. That's the fun part.
46 grains of BL-C(2) with a 150 grain bullet should come close to duplicating 7.62 NATO ballistics. BL-C(2) is a canister grade equivalent of WC 846, which uses the same charge in M80 ball. W748 might come fairly close to this as well.
I suggest working within a +/- 1 grain range of that in 0.5 grain increments and see what shoots the best.