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

This post by @gdonovan has some interesting documentation.

https://www.forabodiesonly.com/mopa...r-with-pictures.178459/page-4#post-1969609303
And he makes the point that to say an A500 and 42RH are the same transmission is bunk.

Functionally they are the same in that the case is the same size, they have the same gear ratios and number of gears, but the parts inside have been changed so that a later trans is maybe the better one to grab.