I agree that "generic parts stores" carry thermostats and a zillion other parts at less than dealers. Also many Motorcraft parts are now made in China so it does not matter, the Chinese make very good quality parts. Being "patriotic" about auto parts is pointless.

in the case of the thermostat, it doesn't matter, buy the cheapest, you need to replace it every 2 years anyway, or as soon as the heater's air temperature becomes lazy. I paid $2.99 for as thermostat 2 years ago and it is still working.

the sensor in question is near the thermostat housing, those need to be replaced at least once in the life of the van.