If your vehicle was produced in Geelong, it would have been 6 volt and equipped with Lucas electrics.
Check your generator, should be a Lucas, model C45PV-4 or C45PV-5 and part no. 22459 or 22477 and marked 6V.
The regulator would be a Lucas, model RB106-1 or RB301 and part no. 37171 or 37165...