If it has an Australian body number was it made in Australia?

US made trucks of that era do not have a VIN by the current formal definition of that term. That standard was adopted in the US in the late 70's to take effect in the early 80's. It is an international standard and was adopted in other countries at various times, at least some of them before the US.

Anyway the titles for many of these trucks in the US have the engine number as VIN and others have the body serial number.

That's US made trucks. I have no knowledge of what might have been the practice with vehicles manufactured outside the US.

And we'll have to hope someone who knows the rules in Australia speaks to the question about getting a title. In the US the rules vary from one state to another and I would not want to even guess what they are in your country.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...