JDM-car-parts.com is offering this http://jdm-car-parts.com/item-for-sale/z432-z432r-fairlady-z-flat-panel/. They're not offering a fuel tank to mach, but the tank doesn't look too difficult to replicate as it seems to be constructed from two end plates and a piece of sheetmetal wrapped around.
This is a picture Kats posted,thanks Kats!
I assume the hight and dept of the fuel tank to be the same as the standarad 60 liter tank so the dimensions are somewhat easy to estimate. It would be nice to know the correct measurements though.
If you have any information on, or pictures of the tank, please post them!
Best regards,
Peter