Fourwheeltravel,
Don't feel to bad, I'm an Australian citizen living in WA, I bought a RRS in NSW, it was impossible for me to legally drive from NSW to WA. I tried my best, the dealer I bought from couldn't help me, and they tried quite hard. Once I left NSW I was not legal on three levels, even in NSW I wasn't legal on two. It was only by the dealer accidentally forgetting to take the plates off I managed the drive without getting pulled up.
Once back in WA I could legally get a permit to drive to the testing station to get the vehicle over the pits and registered.
I insured the vehicle in NSW on NSW plates with me as the owner, had push come to shove I'm not sure how insured I actually was.
What you could try is get the vehicle to WA (somehow) after you've sold your vehicle to a local resident, take it over the pits, you only have to do this once in WA as long as you don't do anything daft to yoir truck or act like an idiot, register the vehicle and then borrow the vehicle off the person you sold it to for the duration of your visit, then buy it back off them when you decide to leave and stick your own rego plates and licence sticker when you get back home. If you sell it cheap enough both ways the stamp duty would be minimal.
Ludicrous I know, however the licencing laws and rules between states are ridiculous, the problem is everybody wants a buck or two.
I wish you the best of luck.

