When I bought the 86 I used to own the compressor and brackets were gone.
Rounded up what I needed cleaned the hoses out with isopropyl alcohol mixed with water, probably 70% alcohol and 30% water and blew the crud out with compressed air. I also put iso/water and blew through the condenser and evaporator.
New compressor and orifice tube and receiver/dryer as Bill mentioned, all new o-rings and put vacuum on for an hour and serviced with R134.
It was still working great when I sold it, 2-3 years later.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona