[Steeveedee]

Six-cylinder-engine powered trucks don't usually have a fan shroud unless they are air-conditioned; they only have a finger-guard. Overheating at idle is generally due to lack of airflow.

Did you do anything with the radiator? Look inside to see what the tubes (that you can see) look like. There could be enough solder bloom that make that an issue. If it sat a long time, I'd just have the radiator rodded (at a minimum) to remove it from the list of things that could be bad, (but that isn't necessarily going to fix it- it's in the assurance category).