i second nightmare's suggestion. rust is the big problem with our trucks --- everything else is usually great! in addition to what he suggested, also look for rust under the battery, and MOST IMPORTANTLY - along the drip rails --- these are the rails that run along the top of the windshield and wrap around and down the back of each side window. these drip rails are always prone to rust --- and once they are rusted, its really difficult to replace them. things like the rocker panels, cab corners, etc. can all be replaced with good body work. but those drip rails are one of a kind. it will get messy if they are rusty.
good luck! i hope you find a fine truck!
jewels.