Rear end changing out.....little info please

[72freak]

I have a 72 GMC short fleet that I picked up from a board member a few months ago for free. It was a nice truck at one time. Big Block (removed) AC, tilt. I am basically putting it together with spare parts that I got with it some of my parts from a few of my junkers.

It obviously has a rear end problem because it wont roll very well. It binds up and just slides. I have not pulled the cover or raised it to see what is going on yet. The truck came with new rear chunk in the box and 2 sets of ring and pinions but they are something stupid like a 462 or something.

I have several complete rear ends in other 67-70's that I can swap out but the lug paterns are 6 and the 72 is a 5 lug rear. I want to stay with the 5 lug of course.

Can I put a complete rear end in it form a 67-71 and then swap out the axles or can I put a chunk form an older truck in the housing of the 72 ?????

I am rear end STUPID so please bare with me on this.

Thanks