Ok, I have been told (ie: have not seen for myself) that the splines on the stub axles (flanges) are different in number from the 260Z R200 to the R32 GTR - the 260Z having something like 29 splines and the R32 GTR having something like 31. Have you encountered this problem? If so, how are you overcoming it?
Have you checked out if it is viable to make up spacers that fit into the crown wheel bolt holes in the diff centre? I have heard about it being done with 12mm holes to fit 10mm bolts, so it might be viable doing it with 17mm holes to fit 10mm bolts.