Diggin in mine and cannot see a connector like that, it's an 1985 shell with a late 1986 wire harness. I have one 4 wire connector somewhat similar that isn't connected to anything either.... What are the wire colors? White with black stripe is chassis ground and I am pretty sure the green wires are for the brake lights or could also be for radio.I am still trying to figure out what that plug/connector is for down by the fuel sending unit.
I do have the original '85 harness buried around here in a tote. If we cannot find an answer easily, I'll go about digging it out and hopefully can get an answer that way.