Doubt you'd be able to do that, unless it is an actual South African import.

Some states the A14 is an acceptable upgrade without engineering approval. Perhaps check if this is the case in NSW?

Other wise your options are;

Run standard A12

Run slightly or heavily worked A12

Bore and stroke the A12 to make it larger capacity.

Grind off the A14 engine markings and change to A12.

Get engineers approval for a mach larger engine for the same cost of the engineers services, CA18, 4AGE, SR20 etc etc