So I swapped a good '79 cab onto my '78 f250. Of course I didnt pay attention to the tail light, brake light, or fuel gauge/ sending unit wiring on the old cab before i pulled it off and sent it to junk. The plugs and wiring are different on the new cab. In the old harness thats original to the truck I have two green wires for the sending unit with no plug, two red wires coming from the brake differential valve (I think thats what it is) with no plug, and a black plug with two female bullet style connectors and two male bullet connectors. Coming from the cab I have a round black two wire blade type plug, a seven wire female bullet type plug and a square green two wire blade type plug with both wires going into the same side. This green plug is the only one that has power with the key off and lights on. The key needs to be on for the other plugs to light my test light. I found where the sending unit wires go but the rest I have no idea. Any help would be greatly appreciated on how/ where to hook up the lights. Wiring diagrams in the Haynes manual arent helpful and I cant find much info elsewhere. I can post pics if needed

 

This help?

1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net