A-904/'68 Valiant Transmission Fluid Confusion

Use what the manual says. That's the original Dexron, which you cannot find. Then Dexron II, which is really hard to find and finally Dexron III, which is what I always use.
Forgive me if I'm not understanding but if this is your advice then the multi-vehicle should be fine, no? It at least claims to be a suitable replacement for dex-II/dex-III so unless I'm missing something, it should be good enough. At least, that's what I'd think. Again this is my first mopar/a body so my apologies.

I'm only so hung up on the multi-vehicle as I already have 4 quarts of it (so I'd only need to buy 2 more, compared to getting 6 quarts of something else).

We're talking about a transmission here that can operate on 30 weight motor oil.
I think this is kinda what I was trying to get at with my original post. I know older engines/transmissions tend to be more lenient/forgiving than modern ones so if that's the case, does the difference really matter all that much?

Thanks everyone for the replies!