According to my logbook I've got 22.6 hours in the accident airplane. Most of the KLA 31s have the BLR kit, however a Navajo bulked out with Amazon Prime, other UPS freight, etc, is going to be about 1,000 under gross. Having lost a motor in a KLA Navajo up around 9,000 feet before, I can tell you that I didn't need to descend until I was closer to an airport.
Running out of gas? Certainly possible. SOP was to top off all 4 tanks in the outstations, operate the evening flight back to DEN, then fly back out in the AM with the remaining fuel. Done right one had about a 90 min reserve on landing. Done wrong, well, who knows. As I recall, taxi, take off, and climb was inboards, cruise was outboards, descent and landing was inboards. Numbers escape me but the inboards are definitely the larger tanks.
If you weren't paying attention hitting the center stop on the fuel selector, the one that says "OFF" wouldn't be hard to do, and apparently the last one that KL put into a field was found with both selectors in that position. If one couldn't figure out how to look down at the fuel selector the moment something stopped running, well, maybe flying airplanes shouldn't be your thing. Or perhaps my 900 hours of PA31 in SE AK has just trained me well. Anyways, the rumor was one of the owners jacked up the airplane, dropped the gear, put on two new props, and flew it out.
The usual morning flight to western KS is DEN-GLD, which a truck from both Burlington, CO, and Colby, KS meeting the aircraft at GLD. If their was too much freight for one airplane the route would be split with one airplane going to Burlington, the other Colby. If I was doing Colby my usual MO was using the standard canned flight plan to GLD, then cancelling and continuing VFR. LYM169 is the canned flight plan DEN-GLD-DEN.