well don't forget the BSM GTR....they have won NSW production car and improved production titles, and the national improved production title in thier gtr, and it is now being setup for sports sedans (has already raced with a top 5 finish).
But yeah if you want to look at GTRs that have raced (door to door) in NSW I only know of:
BSM 32 GTR (originally prod car, then ipra, now sports sedan, about 4 seasons)
Brad's 32 GTR (sports sedan, mra, 2 seasons)
Stu Inwood's 33 (Irace, 1 or 2 races)
Mark's 32 (production car, 1 season)
my 32 (production car, 3 seasons)
roadrace's 32 (production car, previously peter conroys car, 1 or 2 races)
SSS/Geoff Fear's 32 GTR (irpa car, now owned by fernando but not raced since, 1 season)
that's it. the only 7 skylines in NSW that have done door to door racing. as for why not more....dunno!??! I love it! And plenty of people spend way more than me on cars that have never raced. wierd.