Hi Dan,
I think I recognise that Staghound!
The tactical signs are:
1st Pentropic Division: an Australian Regular Army formation of the early 1960s (1960 to 1965, though the Formation sign persisted for some time after disbandment).: Pentagon with '1' within.
103: A Cavalry Reconnaisance Regiment in a Military District, ie a Citizens Military Force (ie the 'reserve', or 'weekend warriors'.) Unit. Used by each of the CMF regiments in each district, ie XLH in Perth, 4/19PWLH in Melbourne (the regular Army Squadron of 4/19 used '103A' to denote the difference), and the Hunter River Lancers in NSW. '103' on the Corps colours red over yellow, diagonally divided.
Your Staghound originated in NSW. However, the two signs are 'mismatched', I think, being an ARA Formation and a CMF Regiment. The Formation sign should actually be something like Eastern Command or 2 Div or similar, rather than 1 Pentropic Div.
The registration number is the original USA number less the 'USA' prefix: all the Staghounds in Australia retained their original US number as the registration, rather than receiving an Australian number.
The '12' superimposed on a yellow dot is, of course, the Bridge Sign.
The only time the Staghound was used by Australia operationally was as part of 1st Armoured Car Squadron as part of British Commonwealth Occupation Force in Japan, and then only for a few months: they were too heavy for the roads in the Kobe area where the Unit was stationed. See my article in Army Motors of several years ago for details and images.
Just had a few days with Darcy and Susan M in Oz .... delightful!
Regards
Mike C