You can take any th400 or th350 trans and run it in a 4x4. You were right on changing the output shaft, and you'll also need the correct adaptor for the t-case you plan to run. The t-case will also need the correct input shaft for the trans you plan to run, as they are not all the same. My two favorite combos are a SM465 four speed manual with a NP205 case. Bullet proof and pretty indestructable. For an automatic setup, I prefer the th400 with the NP 205. Also bullet proof and nearly indestructable. All going to depend on what transfer case you plan to run and what trans you decide on. For an auto, I'd lean heavily towards the th400, but that's just my opinion.