I recently rebuilt my '85 GN's turbo. The compressor seal failed, (or so I thought). Bought a rebuild kit from Limit Engineering and the turbo went together without incident. Installed it on the car, it ran smoke-free for about 20 mins or so.
I then picked up the revs (1500rpm) and...
You should have the outside diameter (o.d.) of the turbine shaft as well as the o.d. of the journal bearings (of course, you'll need to use a micrometer for the measurements). I recently ordered a rebuild kit from Limit. I have enjoyed dealing with them. You won't be dissapointed.