Timmer,
I think if you are loosing steam going up hills then a cam ground for low to mid-range torque would be most suitable. Large cams (lumpy idle) are typically used for high speed operation where the velocity of the incoming charge helps to fill the cylinder, ram effect.
As for the carb, is the truck starving for fuel? If not then more carb is not the awnser, too much carb has a detrimental effect on low-end performance.
What is the rear-end ratio? Maybe a change in gears is in order.
