In reply to:
Yes,,,,,,the outer's are interchangable,,,,,,,,,,,, and much less expensive then regearing the '81.
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He has all the parts.. it's just a matter of what he wants to rebuild. While I'm sure that either axle would benifit from new upper/lower balljoints (rebuilding the spindle and repacking the wheel bearings with new seals), why does he want to rip the axle out and put in the same thing but different?
OK, here's an idea.... rip the axle out.... take it and the other one apart, clean the whole mess up and pick the best parts to assemble the axle you want, new bearings, new balljoints, new wear parts in the spindles.... hmm that's sorta what I did last year... but I just got some used parts off of eBay and a master kit.
Whatever you do.... you don't want to just stick some unknown axle under your Jeep and smack your outer knuckles with disc brake on and call it good.
Good Luck