i also want to convert my V10 to AWD, the most important problem to find a good awd transfert case is the passenger drop side on our square body.
most of the mordern truck (IFS chevy) have driver side drop transfert case, so you can't use one of their TC (denali c3 TC would be have perfect).
so there is 2 solutions :
1) convert the square body to driver side drop by changing the front axle (70 's ford ones are driver side, or a lot of jeep ones also but they are probably to weak for weight capacity)
and then use a Grand cherokee TC (NV242 is for me the best because it alsways have a 2wd mode, or nv249)
2) the easiest way, use a np203 but it won't fit directly to a th700r4, you need and a gearbox to TC adapter (advance adapter makes one).
the bad side is that TC is twice the weight of the other aluminium.
i was wondering, if it was possible to find/build an inline viscous coupler that you put betwen the standard transfert case and the rear axle, at the tail of the output of the tc, or à the input of the rear différencial. but i dind't find this kind of part?
So i choose the np203 way, i must go to bring the TC at home in a few weeks, but the works won't start at once, because i want to do a frame off restauration.