Wiring diagram for 1967 Plymouth AM/FM radio
If it helps any, probably very similiar PCB
1965 CircuiTrace Bendix Radio
my radio rebuilder told me the Dodge model had a light that went on when the dash lights went on, but the Valiant just had a power lamp.
wire the amp as a single channel and then run speakers out the amp through a fader if needed, dont run them in series or parallel off the 3W radio as the amp aint the strongest anfd the impedence will change on the speakers.