5 speed for a 700R4 project

Hey , I have a 91 L.D. 3/4 ton 4x4. It has a 350 and a 5 speed. The 5 speed is the problem. Its too weak, I keep on going through tranny's about every 20k miles.. At 2k a pop that game gets old. I am going to be putting in a mildly built 454 or a nice 383 in there in the next 3-6 months, so I want to get rid of this transmission first. I plan on doing a 700R4 built to the hilt with a manual valvebody.I have access to a core for it now. It came out of a 2wd truck. What will I need to swap out or buy when I build this transmission. What changes will I have to make to make it work. I know a stand alone computer, what else? What will I need to do with my crossmember, or driveshafts? any other ideas? Will the transfer case bolt up, will I need to buy adapters for it? Mainly, what will I have to change with the transmission coming out of the 2wd? Thanks Cody Lee