Most likely it has the wiring for the AM radio, this is four wires, one goes to the instrument cluster lights so it will have power when you turn on the lights, another wire goes to the acc side of the ignition switch so it will have power when the ignition switch is in the run or acc position, the last two wires are the front speaker one will be grounded in the radio and the other will have the audio power to the speaker, the wires would normally be in two molded connectors, one power the other speaker, this is how the 70 is done, I figure the 69 is probably the same. If you intend to install a newer radio, most the speakers are not grounded and in addition the power lead for the radio can not handle much current for a newer radio, but it can work for the ignition or on sense. Good Luck. | 
1969 mustang radio wiring diagram 
