Make sure you stick to the speed limit, they're extremely strict over there and love to hide cameras in unmarked cars / bushes etc.
Nobody is going to rent you a 10+ year old Monaro so that's a non starter. Proper sports cars are insanely expensive to rent so your best bet is going to be something like a Holden Commodore SV6 or a Ford Falcon XR6, they both went out of production a few months ago but there should still be some on rental fleets. You'll probably need to rent from the Premium class to get one.
Yes and I drove my Falcon around it, it's a public road you can drive on
It has a very low speed limit though so don't get any ideas!