2nd Gen automatic transmission A500/R4AC1 information

So I've been scrubbing the internet for a while on information for these transmissions.. haven't found much other than that they're "Japanese copies" of the A500 with a few changes, but not what those changes are other than the bell housing. I'd just like to know if most of the general guts are the same as the A500 to make it easier for a rebuild since there's so many more A500s than r4ac1s.

Anyways, I found this pdf regarding the a500 family of transmissions that seems to say that they were just renamed for the D50/MM trucks.(that I can't seem to attach to this post) And I just dunno, if anyone has more information on these feel free to drop it below. Wondering if when my transmission goes if I'll be screwed or not, a manual swap seems like a lot of work and time that I currently don't have.