If you don't find what you need in Jeep for your friends jeep, why not search junkyards for full size 4x4 trucks? As long as it is a V8, V6 and has the tranny you want with transfer case... the hard part is over. It is simple to weld in mounts and make a transmission crossmember. It is also simple to modify driveshafts to fit your axles. And if you don't know how to weld, it is cheap to get someone to do it for you... as compared to your alternatives.
I have swapped a Chevy V6 (4.3) with an AX15 for its original 2.5 and the AX5 in my jeep. After all was said and done, I thought about it... I wanted to keep the jeep JEEP except for the engine. This was a COSTLY MISTAKE! A five speed is a five speed. It doesn't matter who makes it... unless it is just crud (like the AX5). The "key" is to get everything "matched" from a factory vehicle. That way, you know how to put it in, and how to order inexpensive parts for it. You don't have to worry about adapters or custom made parts except for those already mentioned. I removed my body off the frame and it would have been so much cheaper had I found a totalled Chevy Blazer or S10 with the drivetrain I wanted. I hope this helps. You might want to check out my build. It is listed in the signature.