The "DRAFT" of National Code of Practice for Light Vehicle Construction has been released for public comment/review.

http://www.dotars.gov.au/transreg/vsb/vsb_ncop.aspx

This is the national code that the state governments have been working on for the past six years....to try and get some parity. This is the document that all light vehicle modifications will be managed/processed by in the near future. When it is introduced, all states will finally have the same rules so you will easily be able to buy an interstate modified car.

Things like brakes (vented, dual circuit, boosted etc) should become uniform when doing engine conversions.

Feel free to direct any issues to your respective state road transport authorities....their contact details are on the first page.

Sorry if this link has already been posted, I couldn't find it with a quick search.
Mokesta

PS the Dotars web site is really slow at the time of this posting...