and since my coupe is now 30 years old it's eligible for Special Interest Concessional Registration as a "Classic vehicle", which is $140 for 12 months instead of the normal rego $558.50

I could afford to register all 3 of my Datsuns and still have change left over!

There are restrictions though. You can only drive the car to and from events or club meetings, places of repair, or in preparation for events. You can drive the car within 15km radius of its garaged location anytime for road testing purposes. But I have been doing that for the last couple of years anyway and paying full price.