Overheating problem

[benbloom]

So i picked up this truck that had been sitting for a couple of years, ( i flushed the radiator multiple times before driving ) but now when i drive around the temperature gauge creeps beyond that second line a couple of centimeters or so and will stay there. its basically running slightly hot it seems, unless the gauge is not accurate. thermostat won't change the high temperature, but maybe it is opening too late? where should i start with this?
ive got a fan shroud and the correct coolant amount and mixture. its an AC cab, but heater and ac have been bypassed. any suggestions would be appreciated!
thanks
ben