If you mean the rear axle, everything will just swap over, the leaf perches are in the same place on both axles. You could however save yourselves some work and just swap the 3rd members.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed