What are the most likely Donor vehicles for the A 500 4 speed automatic?

That day in two yards I found a 91 van with a 727, a 91 van with a A500 3-pin and that 93 with the RE. Was really wanting an A518 2-pin. My 91 B300 van had a A518 2-pin.
DionR what is the difference between an A500 and a RH44? Same with the A518 and RH46? Is the A518 a 2-pin and the RH46 a 3-pin?