stock turbo

Here is a link that has very good picture references from gnttypes website.

Turbocharger Photo Guide

Produced by Garrett (Air Research at the time) it was a very good match for the horsepower levels that the Buick engineers were shooting for. 245-280 flywheel hp range. The official name of the turbo used on the '86 & '87 Turbo Buick was TBO-348. It would safely support up to 375 flywheel hp when pushed. Some have made more than that, but the rotating assembly was definitely getting outside of it's efficiency range. It is pretty much done at 24psi as anything more and it starts to super heat the charge air.
As far as the wheel specs, I do not have those, but it is a member of the T3 family of turbos. the turbine wheel is smaller than the T31 Stage 3 turbine wheel, and the compressor wheel is tiny as well, when compared to todays upgrades.

Hope this helps a little.