I need to know which transmission the early 90's 300zxs used in the IMSA race circuit when they were mated to the Q45 V8, after the TT was outlawed. Can anyone answer that question, or point me in the right direction?

I think your talking about the GTO class car run by Cunningham Racing.

Not sure exactly what they used for trany, but I do recall that the twin turbo V-8 IMSA GTX Z run by Bob Sharp racing used a Hewland transaxle mounted at the rear, driven by a drive shaft (at engine RPM!).

Most race car developement usually goes ever onward, so I'm guessing that if the rules allowed it they probably also used a Hewland transaxel (very expensive at about $9K, and requires constant rebuilds).