The only difference that I have noticed is if you are going from 2wd to 4wd as you have to measure and cut the hole in the frame for the shackle mount and add the spring hanger for the front spring, besides swapping in a 4x4 crossmemeber.

1975 Ramcharger 6" lift 35" Mud Terrains 8 lug 44 front, 60 rear. (R.I.P.)
1976 D100 lowered 3" & 5" Now with a 440!!! (sold)
On the hunt for another beauty to build.