Its purely a box ticking exercise to get it into the country under the personal import rules, you will need proof of purchase in order to work out the duties at customs in Aus before they will release the car from the dock.

Its the local registration office that are the awkward buggers that may pull you up on the mods, so keep all the standard parts to swap back if needed, just put them in the boot when it goes in the container and make sure you see it sealed up this end.