"You actually need two distributors, one from the 3A, and one from the 3T or 4K-E.
The 3A distributor is the one you'll end up using, but you have to gut it first, then install the "guts" from the 3T or 4K-E distributor. When you're done, you shoulld have a magnetic trigger mechanical advance distributor that will fit a 4A-G."