There is a difference in the splines between those years (22 and 26 I think), but it doesn't really matter because he is going to be putting in a whole new front axle anyway.
One bracket will be missing, either get it from the dealer or cut it off the 4x4 you have.
I still just say swap the 16v into the 89, probably be easier.
Oh and you would need to swap transmissions too, the tcase you have on the 2wd is just a dummy tcase, and the transmissions are completely different. Unless you got lucky and have the rare 2wd tcase and tranny that are the actual ones out the 4x4, just without the gears. If that is the case you can bolt your tcase right up to the transmission, and use the 4wd driveshaft but I doubt it.
There isn't much fabrication but the bracket that is missing for the front dif will need to be welded on. You will need the complete front axle hub to hub, new front and rear driveshafts, and the 4x4 tcase and transmission. Sounds like a lot of work to me, just put the 16v engine in the 89.
Or go source out a good 8v motor and put that in, keep one trackick for play and one for getting to work.
