69 Valiant Radio Help

Was there not a red power wire on the Kenwood head unit? If I recall correctly, the head units will typically have both red and yellow: Red for main power, Yellow for a constant small draw (to keep the time and radio presets). Also, I think orange wires are typically for dimmer control.

I'm not directly familiar with that particular Kenwood unit, but did it have installation instructions with it? If not, a quick google search might bring up a pdf version of the instructions.