Yes, those old F150's/ Bronco's had two plugs-one for power, etc and the black for speaker wires. With the RCA's hooked up, it looks as though you are not planning to use the HU to run the speakers anyway. So you would only need the other grey female plug that is behind that sleeve somewhere in the dash. Follow back that black plug about 8 inches and you will find the grey plug harness taped with the black harness back there. If you are missing the grey plug, I am sure I have some old ones laying around here if that is all you need. Let me know...