The pulley should only be connected to the compressor when power and ground are are on the electrical coil in the pulley. If you unplug the 2-pin connecter from the clutch (eliminating any electrical problem), the pulley should freewheel, even if the compressor is locked up solid. If the pulley still doesn't freewheel, and the belt still smokes when the engine's running, you've got a locked up compressor AND a locked up pully clutch.
If the compressor did get pooched, you can:
A) Look at getting a shorter belt and eliminating the compressor (thus the AC completely); or
B) Replace the compressor, pulley and clutch, accumulator/drier, orifice tube (the bare minimum parts needed; if a hose has a muffler, replace it too), thoroughly flush everything else, recharge with refrigerant and oil, and pray.
Usually, with that kind of failure, on that old of a truck, ALL of the AC parts should be replaced. It depends, on what you want to spend on the truck, to get the AC back. Replacing just the minimum parts is always a gamble, unfortunately.
Another bummer in the equation, is that a '93 was originally an R-12 system, unless it was converted at some point.
Sorry, it doesn't sound like a cheap or simple fix.