Hi Lionel - you've helped me without actually needing to send me anything. I searched for "VSB14" and found everything I needed here:
http://www.infrastructure.gov.au/roa.../vsb_ncop.aspx
On that page, it notes "Please be aware that the NCOP only represents the technical requirements that must be met - administrative requirements are dealt with separately by each state and territory's administrative guidelines or business rules."
That can only be taken to mean that if your mods comply with all applicable sections of VSB14, that it is legal in all states. Is that correct, or can state authorities still overrule national guidelines?