Probably better off asking this question on an XJ forum . . .
But the swap should be simple. Make sure gear ratio matches front and width is comparable. Probably need to relocate the spring pads and maybe the shock mounts. About the as simple as it gets for swaps. But here's an even simpler option: Cherokees w/ factory tow package came with D44 rear axles in the late 80's (like 86-88). Find one of those and bolt it in.
This subject has been discussed at length in the North American XJ Association forum: www.naxja.org.
The above poster got it right - you want to find a D44 that was made for an XJ. They are scarce because they only were offered for a short period (some say 86-88, others say 87 only). But many have been salvaged when their original rigs were scrapped.
The problem with a Wagoneer rear end is it will be much wider. An easier swap is a Ford rear end (I believe from an Explorer) but again you'll have to look at the NAXJA forum for more info.
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