I've ridden the Townsville to Tennant Creek road twice in recent years and it a good wide road, with an excellent surface. I would go that way, if your objective is the quickest route. There is plenty of fuel with the longest stretch between fuel stops being the 260km from Barkly homestead to Camooweal, so with the long range of an ST you'll never run short. Once you hit the NT, speed limits are 130km/h. On the last trip in May this year we struck massive head winds while heading east, and needed to slow to 100km/h so the Harley's could make the distance. At that speed and with the wind I was consuming 6 liters per 100km.