Tapping into Radio Wires

The one (if any) that light a test light with the key in the on and accessory position for switched.
The one (if any) that light a test light without the key on at all for direct battery.

You can usually come off the cig lighter for the constant power connection, because it's right there and the stereo only uses that for memory retention. (station presets and clock time)

I asked the Wife how she wanted the new stereo wired in her 72 Dart.

1. Stereo turns on and off with the ignition.
2. Stereo does not rely on the ignition switch at all. (I like mine this way)

She picked #1 because she didn't want to have to turn the stereo off manually. (or maybe forget and leave it on)