If the aircraft is USA registered the flight has nothing to do with CASA Australia
Obtain a FAA Licence with IFR rating
Obtain FAA ferry permits, Form 337 for modifications to Fuel system, Overload permit. Navigation, communications, Life Rafts, EPIRB, Sat phone
Depending on aircraft type and inflight oil system maybe required.
After all that talk to the Insurance company; they may have other ideas. There are plenty of 'experts' out there; its not fun, it is very hard work.
Best advice from someone who has 40 Pacific crossings; keep it legal at all times ! Take your time; There will be weather delays at times; be extremely flexible.
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