4x4 experts; transfer case I.D. help

[WIDESIDE72]

About a year go I bought two trucks. One is a 72 GMC Super Custom 3/4 ton 4x4, unmolested, no motor or trans, but transfer case is still there. The other is a 71 LWB 1/2 ton 4x4 with a recently rebuilt engine and trans. I pulled the parts I wanted to keep and now have the parts I don't need as well as the chassis for sale on the parts forum. The plan is to take any good parts and use them on my two other trucks and sell the rest. I got the engine trans out of the 1/2 ton and since there was only one bolt (!) holding the transfer case to the cross member and the bolts holding the front drive shaft to the transfer case were barely tight (!), I dropped the transfer case out. I was planning on cleaning, painting (engine) and re gasketing the engine engine and trans and bolting them into the 3/4 ton 4x4. HOWEVER, I noticed that the adapter between the transfer case to engine is different on the 1/2 ton than the one on the 3/4 ton. I think that the transfer from the 1/2 ton is not original, because it did not look like it fit the cross member right (hence the one bolt holding it in). The transfer case adapter from the 1/2 ton has six bolts. The transfer case adapter from the 13/4 ton only has four bolts. I took a picture of the 1/2 ton case out of the truck to illustrate. I only took a picture of the front of the transfer case from the 3/4 ton, as it is still in the truck. I assume the 1/2 ton has a TH350, but never verified it by looking at the pan. Is the 3/4 ton adpater for a TH400? Just out of curiosity, I measured the distance between the bolt holes on the 3/4 ton transfer case. If I remember correctly, it was uniformly 4" center to center from one to the other. I also happen to have a recently rebuilt 2wd 700r4 from an 82 Suburban. The tail housing bolt pattern appears to be the same 4" as the 3/4 ton 4x4 adapter. Can this 700r4 be used with the 4 bolt 3/4 ton transfer case by simply removing the 2wd tail shaft, or even having a tranny shop swap the 2wd output shaft for a 4x4 output shaft. If so, is the shaft I need the factory 4x4 700r4 shaft, or is it a hybrid part from the aftermarket? Are both these cases NP205? (the one in the 3/4 ton looks like it belongsand has not been rigged like the one in the 1/2 ton. Sorry for being so long winded. I try to explain everything well the first time out.