I've often thought about what food to take on those 4000 km hikes between Adelaide and Port Hedland/Karratha when working up that way. The run between Ceduna and Kalgoorlie (Norseman was just a fuel stop for me.) being only serviced by roadhouses. I'd call into the supermarket at Ceduna before heading west and the same at Kalgoorlie before heading east. Buy enough food for three nights at either end though I would only have two nights camping on average for the 1400k section.
If plans to attend the rally next year workout no doubt I'll be repeating what I used to on previous trips across there.