Ps: reaper, the pulley was all messed up and it had a lot of back and forth play, if it sits at an angle with the tension from the belt it would definitely keep it from moving

 

Turn the A/C off and if the truck starts its a seized compressor. Remember
that the magnetic clutch on the compressor engages the compressor. I've had a problem that the engine was locked solid. Wouldn't start even being jumped. Seized compressor. I know this is an old thread but, this could help for the next time.