chris count it.
by which i mean, jack the rear of the car up. put a tip-ex mark at 12 oclock on the prop, put a mark on top of each drive shaft. then by hand turn the prop one full turn, count how many turns the drive shafts do. divide the ring like a clock, so if the shafts go round say 3 times and a quarter that would make it a 3.25.1 ratio.
the 32/33 gtrs are 4.11.1,
the gts4 are 4.75.1
the r34gtr are 3.45.1
etc.
bernie