Regarding Holden's model codes, you're right, they are strange. They started with VB (VA was a designation given to a design study proposal during the mid 70's, before the Commodore was selected as the basis for the new Holden). They moved at random down to VZ, then went back to the start of the alphabet and are picking up disused letter combinations so that the old and new models overlap - weird.
Holden used to have a code to the letter designations that represented the year of introduction for each new model. It started with the FJ and finished with the EH, because a motor magazine cracked the code and was able to predict that the1965 model would be the EF. After the EH, the letter combinations were really all over the place. The only certain thing was that the last "H" model was HZ.