They wouldn't even know as they didn't build them. The last van GMH/Holden made would have been a Combo, before that the Scurry and the Shuttle. Any of the Holden utes with HBD fitted canopies would be in Holden's build records as a Holden ute, not as a van. There may be records somewhere how many canopies were fitted as HBD installations, but it'd be the canopies themselves that may be rare, not the vehicles - Holden utes were and still are common.