Hi Wayne
It may be worth think about some garden hose (or something similar) around your under vehicle lines, brake lines fuel lines...you get the idea, this will prevent damage from rocks and the like when on rough roads. A spare air filter is almost essemtial when hitting dirt roads, but you have already done the Tanami, you know that.
If I think of more, that haven't already been suggested, I will mentioned them.
Regards
Tjupurula