Maybe we should call them boil plugs or something here?
I guess virtually all Australian engine block casting is using the same tooling as used in other parts of the world. Your old XR Falcon, whether a 6 or 8, was running an engine the same as US Fords of the era.
Exceptions might exist in GM products but even the original Holden grey motor was based on the Chev blue flame 6 pack engine series. I'm not so sure about the red and blue Holden 6's and I guess the 253/308's were entirely indigenous.