I have a Sanden A/C compressor on the zuk, that I've converted into an air compressor. I have burned one up in the field. My current compressor I simply add 10w30 oil to every few trips, and carry an oil bottle if I have use the compressor to run the drill or die grinder.
Engine driven compressors are kick ass. They deliver high volumes and high pressures easily. I run my air system at 225PSI on, and 250PSI off and use a small air tank.
To convert any A/C compressor to and air compressor, you simply need
Input side of compressor:
air filter -> inline oiler (not needed on a York)
Output side of compressor:
high-pressure/high-temp line (stock is great for this!) (keep this as long as possible)-> check valve -> pressure sensor -> oil coalescing filter -> air tank -> fittings.
The pressure sensor is used to power the clutch on the A/C compressor. You put it inline; there is no need for a relay, the clutch only pulls a few amps. Since the Explorer came stock with A/C, you can use the dash switch to turn it on/off.
Do note - if you use the dash switch as the on/off, it will cycle the compressor whenever you have the dash controls on defrost and the two A/C settings.
I also used 3/8" sized fittings on everything; that way, I know the system can flow more air than I will ever need.