Great report - good to hear about the buses in Argentina - looking forward to our trip in September I managed the Cuzco - Puno rail trip in Peru in the 80s and Xining-Golmud in China five or six years ago.
The Prospector should have gotten to 160+km/hr given the track improvements in the last few years. At least it did for me in the opposite direction. Which leads to the question - how did you get from Kalgoorlie back to Perth?
Happy wandering
Fred