DO NOT buy a car from king buyer... they'll rip you off, esp if you're gaijin. The cars on the website are never in stock (ie sold by the time you contact em) and most often prettied up to sell to other countries. You'd be surprised what a cut n polish does to cars in photos.
If you're after a GTR, there's a couple of dealers in japan I can give you addresses to that sell quality cars. Whereabouts are you?
If I were you and shopping for a car to bring to Australia, buy a car that is unique, ie not on the eligible to import list, or too highly modified to be imported under SEVS. I'd say a worked NSX, WRX STi, or a pimped out late model Toyota Celsior (Lexus GS400/450 here) or a JZS161 Toyota Aristo twin turbo with heaps of mods (Lexus GS300/400 here)
Keep in mind personal imports still have to have a very minor compliance process, part of which is an emissions cert depending on the state you're in.