Have you had the engine apart recently?
Does the rad feel too hot to touch?
I'm trying to narrow the possibilities. If the rad becomes way hot, you have circulation. This would mean that you don't have enough air flow through the rad.
If the rad stays cold = little or no circulation. Bad water pump, (although it's new) bad tstat (although it's new). You may also have poor or slow circulation due to a restriction in the system.
Suggestion: from cold, start the engine with the rad cap off. Run the truck and watch for the tstat to open. The coolant in the rad will start moving pretty quickly indicating the tstat opened. The coolant should move pretty well. If this happens, the tstat and pump are working.
Does the fan pull good air? Feel behind the fan (make sure you put your hand in it

) to see if there is plenty of moving air. You don't really have to feel with your hand, the air should be cruising around really fast.
Only other thing I can think of... I have pulled rads and found grass, twigs, dirt, leaves and other stuff (including dead birds) that have partially blocked air flow. Especially if you have A/C. Crap gets stuck between the rad and condenser.
Also, do you have a rad shroud installed?
There has to be a sollution... all it takes is figuring it out. (duh)