Hi Dave,
I would ask Alfa Fiberglass in Victoria.
http://www.motorsportfibreglass.com.au/
When I was in San Francisco I went with a couple of other S30Z enthusiasts to a guy's place who was selling some S30Z parts. He reckons his father did the original moulds in that widebody style back in the day.
The 280YZ kit
There was photos on the wall of their old race car. I have no reason to doubt him. I think he said they sold the moulds onto someone.
Anyway if you're struggling to find it, I may be able to get his contact details again. He was busy turning a relatively rust free original 240z into a race car. Kind of broke my heart, but they are still relatively common over that way.