you want an 89 or newer case. most trucks with a 302 came with an aod. some say the 300 six did not come with an aod, but they most certainly did...
though post 88 the e4od was the standard on the 250 and up and the c6 was an option. most think it was the other way around as well...
i dont remember seeing any 4x4 aod's till after 84, and there were a few different extension housings as well early on...there were like 15-20 trans options a few different years or something ridiculous like that in the 80's and that is why there is so much bad info.
the issue here is the window for a 4x4 is small from 89-93, but the earlier 4x4 shafts and extension housings can be used. converting a 2wd to 4wd is pretty easy.
the suck here though is the aod is a hydro trans, so the b.e. controls re-cal kit is a must do if you do not want to pop for lentech parts. with efi it is pretty easy to hook up the throttle valve, otherwise lentech has some great options if your pushing over 300 hp.
personally, i would go with an explorer setup and a 44 series manual case.
you want a 98 or newer 4r70w trans if possible with a 96 explorer eec setup. but the later stuff is fine, just for sure have to tune out the pats and live with the later fuels systems.. the 44 series t case if you want part time 4x4 or just run the awd case if your just cruising.
the tunability of the eec5 and its natural 4r70w counterpart is a pretty nice package with room to grow.