Here's a followup....2 or 3 weeks ago Discount Tire installed a new set of Pathfinder HT light truck tires, Load E. We towed 3-1/2 hours each way on a trip, and they seem to be fine. I ran 70 psi instead of the 80 I use to run in the Coopers. These tires seem to have a slightly softer sidewall, or maybe the 10 psi difference explains it. I don't know.
I seemed to have a little more wiggle when passed by big trucks. But so far I'm happy with them. The Pathfinder is made in Korea. I also had them put on a new passenger tire for a spare because the original 18-year-old tire was under there. Not the best scenario.