I figure I will update this for future reference. This is on a 92 Ranger, so locations of things may be different on other years.
Everything is literally plug in play minus the compressor relay. The harness for the heater controls already has the two purple wires, which one runs to the ECU and one to the compressor relay plug. Basically transfer over all the A/C components onto your truck, and everything will plug right in. On my 92', the compressor relay control plug was chilling under the power distribution box on the passenger side well. If you look at schematics, all the wiring on that plug are for the relay, aka constant power, switch 12 (from switch), ground, and wire to the clutch itself. If you're wiring in a relay yourself, you need the purple wire off that plug to trigger your relay. To wire it up so the low pressure/cycle switch functions, purple wire from the plug goes to the purple wire on the switch harness. The other wire off the switch goes to your relay. So once the switch breaks the circuit,the relay kicks off and compressor kicks off.
This is a pretty vague description but hopefully it helps someone in the future.
P.S. If you're just snipping off the pigtails for the components at the junkyard, be sure when you're getting the pigtail for the compressor, trace the wires because this harness has diodes in it. The diodes prevent voltage spike in the system, without them, you're risking frying your electronics. So watch out for them and make sure you snip away with them still in tact. The diodes cross over from the positive side to the negative side aka + to - .