Well, what you have to do to make the 72 2wd into a 4x4 is to remove the front suspension and main cross-member. engine will have to come out as well. take the whole front axle, springs, spring mounts, cross-member out of the 4x4(you may have to fabricate a few things but it can be done. Then you will need to adapt/fabricate the T-case/tranny mount to fit into the 2wd. The rear end will most likely be a trailing-arm type suspension and it will need to be swapped as well(some had leaf-sprung rear suspension).
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All in all, I think it would be easier to adapt the 72 body on the 78 frame. It has been done before.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!