There are still quite of few of these door panels around in very good condition. That being said, I would sell them for a little more than what repops sell for. Perhaps $200 more.
Black is a very common color and as they fit Cudas, Baracudas, Challengers, RT Challengers and RT/SE Challengers they are still very much out there. Now if the panels you have would have been a harder to find color such as Blue, Red, Burnt Orange etc, the number still available and in good shape would be much less, and therefore worth more.