These symptoms occurred a few other times. Once on the nightmare trip back from Moab this past spring, but that's a long story for another day. Another time on the Bunce School Road trail (2015?), and on the way back from Boulder in June 2014 both during the late afternoon and at night.
The fuel pump doesn't always cut out on long trips and/or warm days. I had no problems on the way to Ouray and back last year, or on the way out to Moab, or to Colorado Springs, or on any other drive or trail that I've been on in the last three years since the problem started appearing.
I did notice the last couple times this happened that the ECM box in the passenger cabin, and the relays in the engine bay, were hot, while the fuel pump itself was barely warm. However, on the way back from Moab, I noticed this and tried swapping relays and ECMs to no avail. This time, I happened to have my laptop running TunerPro with ALDL connected and the ECM was reporting "OK" status for the fuel pump relay.
This is one of those very rare, unpredictable, intermittent problems that is wickedly hard to troubleshoot...
Meanwhile I'm still trying to figure out how to get the ECM tuned to run well and also pass emissions. I've also got a (new to me) 1911 Officer-size pistol that has been misbehaving.
Don't get me wrong, I love troubleshooting hard problems, but sometimes when problems pile up it can be overwhelming.