Peter,
Did you have any luck finding the engine number. The number that VicRoads have used is not the engine number and you would want to ensure that the right number is recorded for future sale etc as murphy's law will apply.
Have you had a good look below the alloy head, in my car there is a 280 casting in the alloy below the 5/6 plug on the passengers side and then below that in the body of the engine block is a flat area with the engine number stamped in it. See photo right below No. 6 plug. It is quite hard to see the flat area let alone read the stamped number. A torch is definitely needed. Where are you in Melbourne. I am in South Melbourne most mid weeks if you want me to help.
Garry