Hello everyone!!

Is it true that the radio will only work if you have a multiplexer unit attached? I am talking about the AM-FM radios in 1968 model #7303121.

Thanks in advance!!
Clair

No, that is NOT true. There is an adapter plug that should be on your radio on the outside left rear lower corner of the case. This is a round metal "capacitor looking" unit that plugs into a socket on the radio. This is removed when a multiplex unit is used and the multiplex is plugged into the radio at this socket.
The radio does not need the multiplex unit to function. It will play AM or FM but the FM will only be monoral NOT stereo.