The DBA catalogue is a little unclear.
Base model GTRs (R32, all dates) had 296x 32mm discs. They run a grey/green rotor with either nissan or sumitomo brand (can't remember)
Vspec GTRs (R32) had the same brembos as R33 and R34, 324 x 32mm. The caliper is black and has Brembo on it
So, unless you have the brembo brakes, you need the smaller discs. They are still a pretty capable setup compared to most facotry cars.
For interest, R33 GTSt had 296x30mm discs, so in practice the base model r32 gtr and the 33 gtst brakes are interchangeable