Working from fuzzy memories here but I think the canopy was designed by Peter Hughes when Simcoe was the man at Holden. It was sourced to a company in Broady who went broke and I'm not sure who's doing them now. These weren't done by HBD as HBD was set up in a separate plant in Adelaide to do the special bits. I visited HBD when they were doing the dual fuel conversions prior to it being incorporated in the general assembly. I think HBD was somehow part of HSV or something like that and they were doing all sorts of bolt on custom stuff for customers who wanted something a bit special without adding that complexity to the line.
The Sandman Conversion was ordered through the dealer and fitted by the company making them.
Within Holden these were always referred to as Sandman conversions - make of this what you will. If I said to anyone within Holden, my car is the VY Sandman in the carpark they'd know exactly what I was talking about and would go straight to it.
I love the passion you guys have about this though. HK1837 - how the hell do you know so much about this? Are you Ben Stewart in another guise? I am a little in awe.

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By the way, When is HK1837 gunna do a Sandman book? I'd buy it.

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By the way x 2 - The HBD plant was on the Elizabeth site