Hav;

The kit is on its way, but I don't understand your question: "shouldn't the brake light be iluminated with the headlights on? Running lights?"

Brakelights are totally independent of headlights, running lights or directional signal lights...they come on strictly when you hit the brakes (or should anyway!).

Running lights (also known as parking or marker lights depending on where you come from) are a separately energized filament in the same bulb (energized from light switch, ON position 1 and 2).

There are a total of four lighting circuits on the rear of an 1800.
Refer to 1800 wiring diagram: http://www.intelab.com/swem/1800%20Wiring%20Diagram.jpg

1. Running Lights, 6W at each (in)side, 2X4W for license plate illumination.
2. Brake lights, 21W at each (in)side
3. Directional signal lights, single 21W each (out)side
4. Backing lights single 21W in center of license plate fixture

Cheers