"could" be a 60 as I've heard rumor of some 60s being put into a few 3/4 ton Suburbans. Check for king pin knuckles, bigger hubs, larger cover, and of course the "60F" cast into the center section's web. The auto hubs don't mean much as I had a 60 out of an '81 that had them. For the age of the truck, the tranny should either be a TH400 or TH350. Check the pan on the tranny, 350 is square and 400 is not IIRC. The 700r4 did not come out until '82. My guess is that the t-case is a 203 and not a 208, again based on the vintage. the 203 was a full time case and I don't think the 208 came out until the mid 80s.
