You're scooting right on down the road, there. 258 kph (160 mph), eh? Fair to assume you're maxed out?Many parts of Australia have 130kph limits, which equate to 81mph: not too much difference. Much of Europe also tend toward 130kph limits, although places like the Italian Autostrada see that as a guide, not a limit. I moved over for a Fiat with four bulky Carabinieri and a flashing blue light, and I was doing 175kph. I think they were late for lunch?
Getting back to the OP, the Stuart Highway hasn't been unrestricted since November 2016 so there are no unrestricted roads in Australia
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edit to add: this photo on the Stuart Highway is the road: it's not a divided highway but just a two lane country road.