Merv,
The attached web site has R33 GTST specs which has the diff ratio at 4.3:1.
http://justskylines.com/skyline/know...ech_specs.aspx
Sambo thought his R33 was 4.1:1 and I was of the same opinion until I looked up a number of Skyline sites confirming 4.3:1. Now you have found a site that it is 4.1:1. The only sure way is to rotate the rear wheel one rotation and count the number of times the tailshaft rotates.
The physical difference between R32 diff and the R33 diff are the mounting points on the front of the diff. The R32 has small tabs on the front of the casing and no rubber bushes. The R33 has larger tabs with rubber bushes.
The S14 and S15 have the same front tabs as the R33, but I don't know about the number of splines on the drive shafts.
Warren