If staying on the routes identified by the Mile Post, what is the minimal fuel range you would consider being required? And which route would be the worse case?
It's a good practice to fill up at half a tank. It's not uncommon for the rural gas stations to run out of fuel and have a three day wait for fuel delivery.
Also carry enough cash to pay for your fill-up, because it's not uncommon for the debit/credit card systems to go down and if you don't have cash, you can't fill up.