Working on a 71 that originally had headlight washers and putting them back on and need a wiriing diagram since we do not have a harness and not much on the internet.

 

Even if you get a wiring diagram you will need the plugs that hook up to the bulkhead connectors. This generation had all kinds of issues with them mainly the amp gauge wires. A google search brings up a few results but not for 71's. I wouldn't buy a used one if you can find it because it will have the same problems. Unfortunately a lot of the old Dodge truck stuff is just not available. A slim chance you could find one NOS or retro fit in a later year harness.
http://www.madelectrical.com/electri...p-gauges.shtml
Check out some of the plugs here I would bet one would fit the trucks also. Then you could make your own harness.