It is - the Fire Support Vehicle - a Saladin turret fitted atop a strengthened hull. It's a standard Tamiya kit. Biggest critic on this kit was my old man - He pointed out that the jerry cans are US pattern, not Australian, I think the rear fenders and indicator lights are also US styled and the lifting points weren't consistent across the fleet (given they were removed and replaced with strengthened ones too).
He supported these on their trails at Tin Can Bay. They served a purpose (hence their subsequent deployment to Vietnam) but inefficiently. They were much heavier and all the weight was above the normal roof line. The engines struggled with it and failed at a much higher rate and I believe (never looked this up to confirm) they were restricted to firing at a traverse of less than 30 or 45 degrees to the hull axis less the recoil would cause them to topple onto their side.
This kit most closely represents the ones at that trial... as apparently the smoke dischargers were removed in Vietnam and some of the headlights/indicator lights. (Luckily I misted on a tan dust and not a red dust so it's at least been weathered accuractly!!

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