Thanks Phil for the info on age-of-vehicle documents, etc but I was specifically enquiring about existing three-wheelers:
Namely the CJ-based threewheel truck shown:
http://www.changjiangunlimited.com/2007/06-0922-Xitek%20(3).jpg
http://www.changjiangunlimited.com/2007/06-0922-Xitek%20(22).jpg

and the Ural IMZ-8.401:
http://www.ural.com.au/workhorse.html

I imagine that these vehicles may be easier to upgrade to Australian requirements. These include brakes, instrumenttion, clearance lights, and high-mid mounted brakelamp!

With the Xitek that age-of-vehicle documentation may well be still important.

Regards,
John
PS. I have owned a Vespa Ape back in the sixties, Later on I had a BMW R50/5, a BMW R25, and a BMW R75/6.