Some updates.
Will get to Karratha tomorrow for a few days.
Road report-Bitumen almost to Sth Aust border from Cunnamulla and then reasonably good gravel to Innamincka. Cordilla Downs road up to Birdsville was not to flash but bearable. I must have been dead set lucky with tyre pressure selection-29 front 32 back and corrugations were not a problem all the way to the coast except for a bit later.
Birdsville track and Oodoodnatta track are almost gravel super highways where you could easily do 100kph if you wanted to but I kept to 80/90 for comfort and fuel economy.
All bitumen from Marla to Alice and east and west McDonnell ranges and then to Ayres Rock.
The Great Central Road from Ayres Rock is also a fantastic gravel road with some bitumen near Warburton. First half of Heather Highway is average to good but hold on to your hats after the turn off to an aboriginal settlement. The last 35 klm took just over 2 hours to the junction with the Gunbarrel "highway" The Gunbarrel from there to Wiluna Shire boundry is not good. At best I averaged 20kph with I would suggest no maintenance form many many years. Long stretches of the original road are impassable so a diversion track has been created but some times it is so bad another diversion is started and on some occasions, a 3rd or 4th bypass in required.I'll see if I can upload some photos. From Wiluna to Meekatharra and then to Carnarvon are excellent.