The Aussie head has
1.better, longer intake runners which are higher and larger to allow for the Fairlane/Torino size engine bays they ran in.
2. It misses out on the SP and ME Argie heads awesome six branch 4.9 F150 style cast iron header. The exhast port casting is stock US 144-250, except the heat stove is deleted, and it always ran a set of ARD code headers. Stock US cast exhasts won't fit without a heap of welding to fit the Clifford/FSSP port divider, but the aftermarket headers will if the ports are matched.
As for the valve sizes, I have no idea.
Best wishes,
Deano