Found this info on FA. DAMN FMVSS!!!!!

"You may be correct that MOTOREX only crash tested the R33, however they filed a petition for the 1990-1999 Nissan Skyline and got it approved as noted blow (from NHTSA elgibility list):

Nissan GTS, GTR (RHD) 1990-1999 17 NHTSA-1999 5507

Wether or not the cars are the same, (Chasis is probably very similar), the NHTSA bought off on the petition and 1990-1999 Skylines are elgible for importation if made to meet all FMVSS (ahhh... the hard part)"