The '88 will have a litle more room inside, and already has the wider rear axle. Also with the efi it won't stall out as much on steep hill climbs. It sounds like a sweet deal for $300, beats the hell out of the my '86 x-cab I picked up for $600. It needs a complete engine and interior rebuild.

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