Well every state in Australia has different rules - each state has it's own licencing system, so the rules vary ... even though they have just developed a National Code of Practice, but application varies. It also varies depending upon the town you live in (ie. some places are tougher, or stick to the rules without flexibility).
So for example on this awesome beast of a car...the external pull handles below the windscreen would be defected, likely also that the internal fire cables would be too. The rims as well would go in some places...the drift button on the park brake, the harnesses, roll bar, wheel spacers would be defected as well on the road. But like I said it depends on who checks your car.
You should see the wad of permits I carry for mine ... but not all "big spec" cars as you put it are street legal, so who knows if the Aus cars you are referring to are legal street machines, lucky with permits, or running the gauntlet
