Our car is a left hand drive car (originally from the USA). We are used to sitting on the wrong side of the car to drive it now

It just means that you have to drive further back so we can see more, especially when overtaking. At least the Aussie roads are wide enough to take the car
However with some cars they may insist that the car be converted to a right hand drive. Since our car is considered a classic it didn't fall under those rules.
Most people don't bother importing their cars...
Regards,
Karen