Thats incorrect....
R33 Gtst rotors are 296mm x 30mm
S14/15 rotors are 280mm x 30mm
R32gtst/Z32 rotors are 280mm x 30mm
the S15 caliper is also cast iron and the R series are all alloy, i think the R32 GTR is the odd one, i think its a cast aswell... im not 100 % on that though.
im running R32 caliper on an St141 strut etc and 15 x 8 -4 should be sweet but the 10 -12 will be sweet.. see with the factory nissan setup u have to run mega crap offset wheels because of the caliper position.. the rotor height is also rubbish for being setup on an 86/70 . it calls for a more outboard caliper position which means positive offset wheels!, hence why no one use's the nissan rotors.. they use ford and cooper S and their is one more, but ford rotors work great. check out my build thread for pics.
i say scrap the S13 front and mod the 86 front. u can still use the calipers on MX73 or ST141 struts and they bolt straight up (100mm spacing)
im modding the caliper mounts slightly to get it all right but nothing major..