What was the approximate temp outside? Going up a hill? Did you have any heavy loads in the back? Any passengers? When was the last time you had yer AC checked? When was the last time you had yer radiator checked and changed/flushed? Did you check yer radiator fins? How about them radiator hoses? Lot of different things to check...
Is yer truck an auto? Do you have an auxillary cooler on yer tranny? Is the transmission fluid good? Is it at the proper fill level?
When you pulled over, was the overflow bottle bubbling? If not...maybe yer sender/gauge might be wrong. You could test yer temp sender to make sure it's correct.
Does it redline when yer sitting still and with the AC on? Do you have a clutch fan or electric fan?