Rebuilt Engine High Temp Issue

[The Swed]

I should have trusted my gut... the rebuilt engine seemed to be running hotter and told the shop to make sure to put a 160 F thermostat... I have 700 hundred plus miles on the rebuilt and I was hauling a load to the dump the line was long and slow, it was a moving every five minutes a truck length and the engine started to get hot... then run ruff... then quit... I really wanted to dump the load but not at the cost of my engine so I turned around so I could get moving to allow some air flow. I stopped at the auto parts store and I bought a 160 F thermostat and hope they put the wrong one in. Yep they put in a 195 F which is 35 degrees higher. I replaced it but I'm not sure why the engine had such a hard time at the high temperatures. Any thoughts... See attached pictures... the first is the temp gage at 195, the second is at 160, the third and fourth pic is both thermostats, and the fifth is the mess. BTW the temp gage was a little pass the center when the engine shut down so I'm guessing at was around 400 F? I'm tired and I hope this makes sense... As always I'm very grateful for all the replies! Thanks for taking time to read this.