Could someone tell me some causes of overheating? I just changed the head gasket and put a new head on, I am still getting water on the oil fill cap but no water on the dipstick.
It is still overheating, brand new themostat, brand new water pump, what else could it be?

 

Condensation on the fill cap is common on many trucks. It is exaggerated by cooler climate temps, lots of short trips where the engine does not get up to stabilized temps, insufficient PCV flow, and running rich.
While it may be unnerving to see it rarely gets severe enough to harm stuff. If your oil becomes milky then it is time to address a fix, and change your oil.

Additional causes of overheating could be a defective thermostat, a water pump impeller that has loosened on its shaft, blocked coolant passages, collapsed coolant hoses, or a cracked block.

 

How are you determining that the engine is overheating? The factory gauges are not the most accurate. See if you can obtain a hand held infra red thermometer gun and point it at the thermostat housing.