"I'm surprised there's nothing more extreme in Australia. I'm in Adelaide, and we have road cycling events with 4000m climbing in 140km."
There is.
"completed the gruelling challenge in 37 days, 20 hours and 45 minutes, pedalling more than 377 kilometres a day ... On one occasion I rode right through the whole 24 hours and we got through 506 kilometres, "
Sorry, I should make it clearer. I used the word extreme to designate hilly. In the context of the original poster it's pretty clear:
From the OP: I'm planning to compete in a 75km race with 4 1000 meter vertical assents in October. This is about as mountainous as you can get in Australia. This is a walk in the part compared to the races in Europe, New Zealand and North America.... I look at the course profile for that, and the course profile for the 4 1000m assents for the 75km race I'm doing in October
The whole point is that you don't need high altitude to get extreme elevation change in a race. I'm more familiar with cycling, but in that sport there are probably only about 4 or 5 rides in the world we can't match in terms of hill climbing, and those are either extremely long continuous climbs (eg, Haleakala, Alto de Letras; our longest is 30km) or 10km+ at extreme gradients (over 10%; Mount Zoncolan, Alto de L'Angliru; out longest is around 9km).
Generally you can make the race harder by looping it over steep terrain, just like the Barkley does.
I was hoping the OP could enlighten me as to why we don't have trail runs in Australia that are just as challenging.
There is.
"completed the gruelling challenge in 37 days, 20 hours and 45 minutes, pedalling more than 377 kilometres a day ... On one occasion I rode right through the whole 24 hours and we got through 506 kilometres, "
You can read about Queensland Policeman, Dave Alley here ~ http://www.abc.net.au/news/2011-11-04/man-cycles-round-austr...