That is a really lame 302. Hope you plan on a rebuild before using the engine. That engine is probably as weak as they were ever made. Something like 125HP when new.
The AOD did exist, not sure if the truck got it. I think it took a few more years until the truck got that transmission. Now the bad news, that vintage AOD is junk. There were fundimental flaws in the oiling system that starved the planetary gears of oil. Even if it is working, it is likely highly damaged inside. AOD has linkage to the carb only, no vacuum modulator. Vacuum modulator is a 3-speed.
More than likely it will have a 3-speed automatic. C4 would be good, but will still need a rebuild to put a 4WD tailshaft in so it can have 4WD. C6 is more likely and if 4WD what I would expect to find. If the bellhousing is removable it is a C4, if not it is a C6.
Being a free truck, you have to decide what parts are good enough to use again.