You’re going to get different answers from many here, but I have had multiple customers with 80’s run the Vavoline multi vehicle ATF with good results. I usually use Dex 3 or Dex 6 for all of the early Toyotas that I touch. To each their own.
Well first thing I would recommend is proceed with caution and prepare for the worst. The warning signs to look for are brown to darker fluid which can indicate a lack of maintenance with the transmission and if your fluid is dark to black and smells burnt your trans is probably headed for a...
In my experience with 90's-2000's Toyota SUV's with the bulletproof 4-speed slushboxes, I have never run into an issue of doing a full 10 to 12 quart fluid exchange with Dexron III or Dexron IV and had any issues. All of the tranmissions that I have done this to had decent quality pinkish fluid...