Drivetrain advice for engine swap

I was wondering about the same info to put into my 71 Duster with a 440. I happen to know someone who has several rear ends & I had planned on asking here which one to ask him for. As far as the moving the spring seats on the ford 9" what if you moved the springs in for a minor tub?
Is the 8 3/4 a better option that a 9 1/4?
sounds like the ford 9" would be the easiest, but I don't know if I can put ford parts into my Mopar.