Heat can be an issue but I’m not sold that the fuel gets hot enough to damage the pump. I was moving the M3W from Arizona to California about mid May of this year. I stopped for fuel just outside Blythe, Ca (right on the Colorado river) and all had been fine to that point. The temp was over a 100 degrees F when I left Phoenix and 105 F at the gas stop. I was there maybe 10 minutes and then I fired up to leave, engine started normally but as I headed up the ramp, it cut out for a second, picked up again, cut out again and then repeated the sequence a third time. I figured I was toast, mentally cursed the Morgan and prepared to coast to a stop and call AAA. At this point it kept running... I figured “what the heck” and accelerated onto the freeway. It never so much as hiccuped for the rest of the trip (another 200 miles). Upon arrival, i discovered that the bevel Box had gotten warm enough to puke some oil out the breather, never had that happen before!
I wish Will the best for the remainder of his journey, he is currently running through a really pretty part of the country (grew up in Oregon).