Whats the weight of the vehicle? (As on the rego papers)
In NSW it equates to CC's = 4.82 x weight in KGs for NA over 1100kgs, or 4.00 x weight in KGs for Forced Induction over 1100kgs.
For under these weights the mulitplication facotr drops considerably to 3x and 2.5 times from memory (I have forgotten the low weights..)
I believe most states are now adopting these rules (Becoming Australia wide inside a few months from what the local RTA engineer was telling me)
(Hence my dilemna in finding a vehicle to house a forced induction 5 litre v12...that still looks sexy, and handles!)