A-904/'68 Valiant Transmission Fluid Confusion

I might be confusing myself, but what's the consensus on trans fluid for the a-904. As a big note to all of this, I'm not interested in what's the absolute, definitively best fluid to use. The debate is interesting and all but I'm really just looking for something that works. Ideally I'd like to do a manual swap in the future anyways so as long as I can fill up and drive without major issues, I'm fine with that.

I read through some forums some weeks ago and although there was lots of debate, between what my manual says and what I read, I ended up making myself choose between dex/merc and multi-vehicle. I bought multi-vehicle (I couldn't tell you why I chose this over dex/merc but I did, maybe it was cheaper) but I didn't get enough as I already thought I had some. I was just about to reorder some more but I wanted to make this post just to clarify.

The manual (on 21-46) says "A-904: Pour six quarts of Automatic Transmission Fluid AQ-ATF Suffix "A" or (dexron)".

In looking through this and other forums, I saw a lot of people mention dex-II/-III. Both Dex/Merc and Multi-Vehicle say they are compatible replacements for these types. My multi bottle even says right on the front "[for] where dexron-III/Mercon are specified". Dex/merc brands online also claim to be compatible with dex-3/merc.

So give it to me straight, am I making a mistake buying more multi-vehicle or is a lot of this debate just arm chair trans experts going back and forth over what is the best of the best tranny fluid for these transmissions? Thanks