[HO455]

Posting some photos of the fan and shroud may help us.

What diameter pulleys are on the crankshaft and water pump? Maybe someone swapped some under driven pulleys some time in the past.

Do you have an overflow/expansion tank?

It's possible you have air trapped in the engine. Have you tried idling the truck with the front end raised 2 feet or so? This helps trapped air bubbles to get out.

Are you seeing a lot of micro sized bubbles in the coolant?

Have you verified the accuracy of the temp guage?

Not the best photos of my fan fitment in the shroud but hopefully it will help.

Whether or not you have a shroud determines the fan distance from the radiator. No shroud means the fan needs to be close to the radiator. With a shroud installed then the fan needs to be at the outlet of the shroud.