ID tag won't tell you if it's an 8.5". The tag warns to use limited slip oil, if so equipped.
The build sheet should show G80, if the LS is there. [Not on the sheet?] Don't know that a 7.5" was even available w/ LS.
If it's a "gennie GN", it would have not been built w/ the 7.5", but could have been built, w/o LS.
My 86 frame is out of the car. If you need a dimension, pic of the 8.5, let me know.