Remove a 3-spd MN/T-CASE, THEN put in 700r4 & T-Case Swap

[archlab]

1971 BLAZER:
I hv a non-standard engine/trans setup in this Blazer. It's

Engine: 400cu V8
Trans; 3-Speed Manual
T-Case: ?

I think the previous owner swapped in this 400/3spd from a 1980 or so K-series pickup. Recently, the 3-Speed has lost 1st gear & is clanging' around, so it's probably GAWNnnn...

I wanna swap in a 700R4 & T-Case. I have a guy that wants to sell a good 700r4 WITH T-Case (is that a NP208?) from a late 1980s-ealy 1990s 4wd truck.

I'd like to just swap in both the transmission & T-Case - not crazy abt ghaving to go through the expense & effort of adapting to fit my existing T-Case.

The MAIN QUESTION:
What do I need to do to successflly swap in the 700r4/T-Case?
* Drive Shaft mods?
* Mounting Issues?
* Linkage?
* etc, etcetc????

THANKS A LOT, IN ADVANCE!