Which part of Australia, as already noted it is quite big...see below.
That said the classic scene is huge for both bikes and cars. If you search on my Gingin, Pinjara and Cottesloe Car show pictures on here (all in WA) you'll be amazed how many there are and how many cars attend each. I think it is down to the climate, in that they can be used, and do not rust! Also with so many expats (at some point in their history) the cars have tended to come too.
Each state has slightly different rules when it comes to getting a car on the road but the import rules are the same regardless of state.
