Ohhh. Alright. I thought you wanted to swap in an AX-15 but if changing the main shaft to a 4x4 version then just trade or buy a junk yard 4x4 tranny that'll mate to the NP231. As for mounts, my experience is cut them off of the doner truck and use them but it depends on the situation and if there is any aftermarket support avaialbe.
I'm planning a 4bt swap in my project jeep...this is all stuff you have to research and findout yourself, especially for doing an odd ball swap like this, that not many people have done before. Google and the search on the forum does wonders, my best be for you is to try to find someone who has already done the swap and listen to what they have to say, if you cant find anyone search each and every part and figure out what it's going to take to make them all fit together and then fit in the jeep. Also find weights and demensions on stuff as well...it's all about the details with swaps and your the only one that can fit the swap to your needs and wants.
DD- 1995 YJ 2.5L, Cat delete, 19lb injectors, 30/9.5r15
Trail Rig- 1994 YJ 4.0L, Rubicon Express 4.5inch lift, 1inch body, D30 Aussie, 33/12.5/r15 Cooper Mud Terrains, front bumper, rocker guards