Stock gears in a 98z?
 

what size are they?

With a M6 there are going to be 3.42's that is the only gear they put into M6's I belive, And in a Auto they are going to be a 2.73's or 3.23's. GU2 means it has 2.73s, GU5 is the optional 3.23 for autos at least that is in the F-Body's ;)