Hi Ken, Holden certainly built quite a few of these for the Military during the war years and then other Government departments like postal, water, electricity etc.
Here's one that I've planned a project for in the past.
They are not particularly rare but are certainly something that the hot rodders snap up if they're in half decent condition.
They interest me because the commonality of parts across a few years.
I thought that all the Maple Leafs were a standard cab rather than the extra cab... but don't know enough to be sure.