[xb-60]

TassieCobra,
Your best route for deciding on engine selection is to talk to your local Cobra community. They will tell you what you can and can't do legally.
I'm starting to feel like an advocate for the Victorian Cobra Club here - your best bet is to (if you're not already a member) go to a club meeting and talk to people who have started down the same path as you. Theirs would be the best advice you can get if you want something you can drive legally on the road.

Cheers!
Glen