Your current issues are only the tip of the iceberg!
There are a multitude of regulations that will cause you grief bringing a US speced 5th down to Aussie!
These range from compliance to Australian design rules,appliance approvals,wiring compliance the list goes on and on.
If you dont intend to use it on the highway or in RV parks or resell it then its not quite so difficult.
It can be done but its in my opinion not worth the money or the trouble unless you are in the industry.
There is lots of information if you search on this subject from organisations and people who are or have considered putting themselves in your situation.
One solution may be to take it to an experienced importer to see if they will do the conversion job for you.
I hope you get a happy outcome!