In Victoria, Australia, a high powered vehicle is classed by VicRoads as:

A vehicle with an engine larger than 3.5 litres per tonne (0.0035 L/kg), or roughly 213.5831564661 cubic inches per tonne. This is the size to weight ratio.

or

A vehicle with a power to weight ratio of more than 125 kilowatts per tonne, or 0.125 kw per kilogram (see Kidas's writeup on power to weight ratio for some good examples)

These cars are not allowed to be driven by people on their P Plates, who are usually young adults between the ages of 18 and 21, although people on L Plates (Learner drivers) are allowed to. This is probably a good idea - people drive unsafely enough with the Commodores and the like that they initially get, without needing an overpowered plastic matchbox car like a Subaru WRX. However, this prevents me from being able to drive my dream car (1973 Ford XB Falcon) until the year 2005, as the car weighs about 1250 kg, but has an engine larger than 266 cis. Mind, it's not much bigger, and the fact that it falls into the criteria of being high powered is negligible, being such as old car. Many newer cars are far more powerful yet do not come under a HPV specification. Perhaps the system needs a re-think, but a case-by-case ruling would be an unnecessary cost. I guess I'll just have to wait.