d1rtyrb - car modification laws vary state to state in AUS, but are generally much stricter than what we have in NZ.
in NZ you can certify practically any modification, as long as its safe (certified) and meets emission standards.
In AUS, all modifications need to be ceritifed by an engineer, and you are limited in same ways to what you can actually do (e.g power/weight restrictions, noise restrictions, etc...) - it's just a No, period. Also correct about the wof thing, things work differently in AUS - but in AUS it costs a LOT more to have a car on the road as it does in NZ.
Make sure if you are going to modify a car in AUS that you consult with an engineer as you go along, that is the easiest way - and will avoid some majorly hefty fines (penalty's for illegally modified cars are much higher in aus than nz) and remember if you're unsure if its legal or not, it probably isnt