There's 3 of them here:
Have a look at http://www.gruppea.com.au/ho.html
Wayne Draper done design work for the HO
He might know about numbers produced, you can send him an email
Some of his work:
Partner in Homologated Options (HO) for:
* The design of police utility vehicles for prisoner transfer based on the GM Holden VR Commodore using modular components and accessories for ease of reconfiguration and transfer between vehicles. (NSW and Victoria Police).
* The design and project management of all aspects of the production of a supercharged V8 Allan Moffat-HO Special Vehicle, including engine and suspension specification, internal fittings and body components. This vehicle sold in Australia and NZ and was considered by the motoring press as the best performing road going Falcon ever produced.
* The design of body components for the Ford Capri Special Vehicle HO, Falcon Station Wagon HO and the Falcon Sedan HO.