Is there something else that may be causing this other than radiator, fan, and water pump? For example, a transmission problem or dragging brake?
When the engine is running, what does your IR thermometer show when you point it at various parts, like the radiator, water pump, coolant intake hose connection, and coolant discharge connection?
Do you have a transmission temperature gauge? If so, anything abnormal?
After you drive it for a while, what does your IR thermometer show when you point it at the brake drums?
2004 Holiday Rambler Scepter 40PBDD
Roadmaster Chassis w/Cummins 350 Turbo Diesel