All 7 1/4 rears the same?

The rear end in my car, 68 valiant, has been rebuilt, no brakes, lines, cylinders, seals bearings gaskets, fluids, etc. the sure grip I am buying is a 22k mile rear ens, 3.23 gear. I was going to just take out the parts need and swap them over. Sure grip, and gears. That’s my thinking since mine has been gone through.
New breaks