As long as the rear is in decent shape, that's the easiest mod there is (you lucky b@#$d!) Get a set of new gaskets, unbolt the ujoint at the front of the pinion, unbolt the axle hub flanges, unbolt the pumpkin, reverse to install. It's heavier than just the R&P, but a lot easier. On my 3600 (if I could find the rear) I wouldn't even have to jack up the truck or remove the wheels. Just go underneath.
Good luck, and don't drop it on your toe.
Peter
Current fleet (subject to change w/o notice) \'49 GMC 3/4-Ton , 60 Austin Healey Frog-eye Sprite (some assembly required), 2011 Dodge Avenger, 2015 Jeep Cherokee. No, they don't all run. My other ride is a (B737)no, (B767)no, A320.... Update... was Embraer E190, now Boeing B787. Knowledge is a wonderful thing, but ignorance means you don't know you can't do something.
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