4cyl trans will not bolt up to a 4.0L V6. As for a 4wd conversion. You'd need to decide how much work you'd like to do. You'd need a 4wd trans, and also you'd need a transfer case. To change tailhouses, you'd need to disassemble the trans to swap output shafts, just easier to find a 4wd trans. Secondly depending on what you intend to use the 4wd for, you'd have to decide, SAS, or stock. Next once you've done that, you'd need to swap the front engine crossmember out for a 4wd one. At this point a 4wd rolling chasis would be just easier, and swap your body and powertrain on to it. You'd need quite a few parts, and some time depending on your skill level to complete the swap.
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