If its an R33 GTSt then buy locally... there's so many of them here that no one who wants to sell one can seem to give one away. You'll save maybe $500 by importing one. An R33 GTSt Series 1 is worth about 10-13,000 and a series 2 is worth between 13 and 16. An R33 GTR will run you about AUD$25,000 for an early model. an R34 GTt will cost you about 20,000 and an R34 GTR anywhere from 40,000 upwards.
If you want anything other than an R33 GTSt or an R32 GTSt, then there's fairly substantial savings to be had by importing. However there's a 3 month wait for one to be delivered to your door from the moment you buy one. If you planned forward far enough you could buy one in Japan right now and start the import process so your car is waiting for you or arrives here around the same time as you.
Guys in teh UK have a very big advantage over the aussies when it comes to buying cars in Japan due to your strong currency.