If you are running hot only while sitting still or in stop and go traffic it should be an airflow issue across the radiator. What fan arrangement do you have? You need to have a factory style fan and fan clutch arrangement with a shroud that fits the radiator nicely. If you have a factory style setup the fan clutch may be worn out. They are supposed to "grab" harder and pull more air when they get hot. Some of the aftermarket fan clutches are tighter than originals and pull more air all the time, but that reduces fuel mileage a little.
If you put gauges on the air conditioning you can determine if it's running too high of pressure on the high side. If it's getting much over 250 psi on the high side the temperature will be getting too high as well. But if there is an airflow problem this will cause the pressures to be higher as well. So put a household box fan in the front of the truck on high speed, sitting at idle with temperature climbing too high, and see if it helps cool it back down.