Does this have rear disc with separate e brake?My 99 has this set up,its a pita.If yours has this remove the rotor and check that the e brake linings are still bonded to the shoes.
The OEM shoes are notorious for de laminating,the glue they used apparently didn't hold up very well.
With both calipers removed use 2 lug nuts to hold the rotors square on the hubs and adjust the star wheels from behind until you can hear/feel them making contact.
This can be a bit of a pain if the truck has awd and/or a posi rear end,there is some drive line resistance and slight drag from the other shoe,chock the front wheels and place the transmission in neutral.I use a small bar between the 2 lug nuts to turn the rotor.
When it feels like both are making contact equally push the e brake pedal down a few times and recheck,don't be surprised if it gets tight then on the next try it goes to the floor,keep re adjusting until its firm every time before reinstalling the calipers.