Tell them to stop running the truck so hard when it reaches an e32 (first stage over heat), which it does about 220 F. and not keep running it once it slows down (at e32, the max engine rpm should be around 1300 RPM, limp home, at e33 [about 230F], the engine may shut down or just idle, but they -HAD- to notice the e32 slowdown and just keep pushing the unit hard.
This time of year, I would also be checking the inching cable and bell-crank. that bell-crank can stick, not all the way out, making the inch spool act as if someone is riding the inch pedal and slipping the transmission clutches until they over heat. take the bell crank apart and grease it up.