My 1979 Dodge slant six with 3 spd. manual transmission could use either fluid in the transmission.So, 80W-90, Dexron III, or perhaps a blend of these two? THANKS.

With that choice, I'd probably go with the 80w-90. More choices, and most likely, a tougher blend for use in the tranny.

I would use the 80W/90 in this application. Do not blend gear oil and ATF.

My AF calls for ATF only, no dino or EP tranny oil, maybe it could do with non EP boron based tranny oil like Chevron Delo or Mobil I, for your app I would suggest dino unless you intend to operate in colder regions.

I'm "up here" in Minnesota,so I decided that dino Dex III trans. fluid for my manual trans. is the best choice. Thanks much for your input.