1996 f-450 overheat 460 engine

Having trouble with this thing overheating change the water pump change the radiator all looks good .
I also scoped the cylinder walls could see carbon on the top of each cylinder all cylinders look the same all cylinders have 120 PSI compression test
I've got no idea where to go from here.
Do not see any bubbles coming up the radiator
Truck only gets hot when you work it hard.
Tell me what else you need to know thank you

 

Have you checked to see if the thermostat is partially blocked? Checked timing?

 

yes I have checked both 10*with spout out and no thermostat. thank you

 

Not familiar with the truck, but mechanical fan? Could it be that the fan isn’t as good as it once was?

 

Is the plate on the rear of the water pump missing?