Welcome Pete,
In answering the paramount question - Can you complete & register you DAX here in WA? - Well the answer is "yes". There are other DAXs registered in AUS so the precedent has been set.
The problem will be obviously to comply with the local ADRs, and these can be somewhat "subjective" in that they can be "interpreted" differently by "engineers" & the "assessing traffic governing body".
In short your best move would be to contact a local engineer in WA and seek there advice. They will be able to outline the do's & don'ts.
In the mean time you'd do well to familiarize yourself with this website:
Australian Design Rules
I believe the 3rd edition is what we are currently up to (see below). Your engineer will better assist you than I can here .
Third Edition Australian Design Rules
There can be a bit of maze to negotiate through, but don't let that put you off.
Enjoy & I'm sure you'll find the weather in WA more conducive to Cobra building & driving.