Ok, newbie...but know my dodges!
The 1/2 tons came with the fulltime D44 standard, but also could have a parttime (hubs style) D44 if it was ordered. The fulltime bearings are noted as weaker, but if most people study the design, it is very similar to that in the 94+ dodge trucks...with the exception that you can change individual bearings in the older model as well as grease them externally through a hole and a grease fitting in the rotor. I believe if you keep these greased they will give good mileage (I think dodge got a bunch of bad bearings when these were built). Most 1/2 tons came 9.25" Corp (which is made by Eaton from what I have read, not AAM) although, some had 8.75"ers and some actually had a semi-floating version of the D60 (very rare and an RC option only I believe).
3/4 tons could have either a fulltime D44 or a D60 with (get this for strength) drive flanges instead of hubs. If you got the D44, then you get a D60 rear. If you get the D60 front, then you get a D70 rear. I believe the D60 front was offer primarily on ClubCabs and the four door cabs. The D60 front can be converted to hubs easily from what I have read.
They also had a single rear wheel 1-ton. D60/D70 combo.
T cases, fulltime = NP203, loads of miles usually mean a stretched chain. parttime should be a NP205 all gear driven...the dodge 205s are the best versions of any of the 205 (chevy, dodge, ford)since they have a large input shaft.
Tranny, yep 727...make sure they don't try to sell you a 904. You can also change it over to a four speed (either a NP435 or NP445) and get rid of the auto (find a donor truck for the swap parts)
When you do the tranny (auto), make sure you know what CID (ie. 318 or 360) your engine is...the torque converter is balanced differently for each. If you run a 360 converter on a 318, you will blow the #6 or #8 (?) rod out the side of the block...and you won't get any warning tha you have installed the wrong converter. This goes for the flywheel of a manual also if you go the swap route.
Not trying to step on toes here, but thought I would just add some more thought to some of this. Also, keep in mind, with a truck this old...someone could have swapped some major parts already leaving you guessing as to what you actually have!
good luck,
steved