Welcome to 4x4Wire, Tanner!
The 89 model has some specific parts for that year only. These items include the ECU, distributor, EGR tube, and other things. Either from an 89 Montero V6, or another Raider V6, you will be able to source the repair pieces. Your grandfather 'should' give you the chance to evaluate the vehicle before purchasing it, I'd think.
I won't pimp the pieces that I have too hard, but I am one of the parts guys here.