I went down to the wharf here in Kobe 2 weeks ago to see my Pajero, and while I was there I inspected about 6 `89 GT-R`s, and drove one. Basically, they were *used*. The one I drove was ok, had some rock-hard coil overs fitted, but the gear shift action was sloppy as, there were squeaks and rattles while cornering, and scratches, small dents and what have you on practically every panel upon closer inspection... oh, and it had previously been in an accident. On the up-side, the engine seemed solid, no leaks, had a few mods and it pulled really hard.
A mixed bag really, but try and budget 800,000yen ($10,500) for the car at auction. That should get you a decent one for sure.