If I remember, this would also mean it would have the "Stereo Multiplexer" in the back of the rear seat, correct? I seem to remember reading in the FSM that contraption was part of the hardware for the stereo system, compared to the normal mono radio. Would you even need a higher amp rated alternator for that setup?
Their seems to be some debate on weather the radio is a 67 or 68 because of the round knobs...the 67 faceplate has a different design than the 68...so a round knob must have been optional in 67... I will post better pics of radio and cars fender tag later today and maybe we can figure it out!