If the first gen has/had buckets then it should be a direct bolt in, if not then you will haveto drill a new hole for the front inners and possibly one for the rear inners. The outer two will bolt up. You may have to raise(shim) the outer rear mounts for the seat backs to be level.

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