70 suburban rear end swap question

[67Mach1]

I am about to purchase a 1970 suburban. The front brakes have been changed to five lug disc and the rear are still six lug drum.

Would like to change to five lug? what are my options using a donor rear end or I have heard about only swaping the shafts and drums. Is this possible?

Also, Heard that the 71-72 rear ends are of a different width than the earlier ones too, is this a myth or reality?

thanks,