And the answer is.........
Regulation 8 as Benji referred to earlier.
We downloaded heaps of info on the comparison in power and how the 280z was also manufactured in 1977 in the USA.
Even copied an ebay advert for a Haynes manual covering 240z,260z & 280z.
So we got it registered this afternoon.
Thanks to all you guys for your help.
Here is a foto of Cam & ! with our girl. Took seven & a half years, now we can enjoy.
We will be getting better wheels and finishing off things but for a while we will just enjoy.