Not sure if what you asking/stating, is that you are looking to do a full drive train swap or trying to convert your rig to civilian parts and keep it stock.
The 302 is pretty much a stock engine for the era it was built, with the exception of. Water proofing. Lots of old hot rodders out there using the same motor. If you are wanting more power out of it then there are things you can do to the engine for that. Larger carb jets, port and polish, advance timing a little, bore the cylinders, yadda yadda.
Tranny options are zilch! You are stuck with the stock tranny for that application. You can most certianly drain and flush the tranny and use modern ATF, most guys go synthetic. Problems arise with doing this is the newer tranny oils tend to be thinner and thus leak out of the tranny. If you don't mind your truck marking its territory and having to top off the fluid more than usual fly at it.
If you are looking for a more modern drive train alltogether then a drive train swap is in order. I suggest reading Gunfreaks threads, very informative and detailed. He really knows his stuff!
Another person to talk with is Tom at Alpha Heaven, he has done just about every swap you could think of to these trucks.
My two cents take it or leave it.