We ship aircraft and helicopter engines to and from the USA and even the ones straight out of overhaul are considered dangerous goods because they ran once with fuel / oil in them.
There are different categories of dangerous goods and teh mis will probably cover it, its a whole lot better to take a short while a cost to get it in to this category than get it bounced / rejected and all sort of hassel
I dont know if USPS have ability to do this, we use DHL for shipping our engines in proper metal (usually) shipping crates
if they use a wooden box, its possible that might not be allowed in to AUS either unless it is stamped with the required markings saying its treated specifically - I don't know much about that
Hay Ewe

