Used to be nations cup I think, had 3-4 different classes.
With V8 vs 4 cyclinders, they have split them into classes.
Classes a to c

I actually went to Eastern Creek 2 weeks ago and watched them (race that was on SBS today) great racing and when in pit lane you can speak to the drivers/team owners and they are top blokes.

To bad they took out the Ferrari's, Lambo, Vipers etc and put them into a different class, it was fun watching smaller V8's hammer the Monaro!