Frosty
For any MA (Motorcycling Australia, and that includes the Victorian arm of MA etc) sanctioned event across Oz the rules are the same.
If you are under 16 (junior) then its a limit of 125 2 st or 250 4 st (would'nt a methanol 250 4 stroke go)
16 and over is senior so you can ride what you want.
Go the big PE in the Vinduro.
Get a TM250 for the pre 75
Get an elsinore for a practice bike
And if you really want to get serious - get your arse on a sidecar
Cheers Steven