Been fighting this same issue with my Dart for a long time. Got to the point where I wired a lamp inside so I could seen when the lights were stuck on. Careful using your foot to pull up on the pedal, I almost pulled the rod out at least once.
While I agree that a spring on the pedal is not the right solution, I finally resorted to the same (actually using a rubber band currently). If you use a spring, remember not to use too much tension as it is only that "O" ring like piece that is holding the push rod in.
I think the real issue with mine is that the bracket is metal fatigued and flexes just enough to not turn off the lights consistently. Probably a result of the pedal being pulled back when the master cylinder was replaced.
