An easy way to check for full circulation in the radiator is to run it up to operating temperature, shut the engine off and with the palm of your hand....feel around the whole radiator. A clogged radiator will have cool spots as well as real hot spots that are detectable by this simple check. You didn't mention if the truck cools off when you're moving or if it always stays hot, if it dumps water from the system.
I've found that once you get the cooling system clean and flowing free with a 50/50 mix of antifreeze and DISTILLED water, that the addition of a 15" 6 blade aluminum flex fan moves a lot more air than the stock fan.
