4x4 12 bolt rear end, same as 2wd rear end???

[mx jim]

I Have a 70 chevy 4x4 with 12 bolt and 4:10s. I wanted to get a new rear end because mine is going bad, but i was woundering if the rear end out of a 2wd is the same as the rear end out of the 4x4?? Also can i get a 5 lug rear end and take the axels out and put my six lug axels in it? Thanks for all the help james