Don't know about the Overlander ... however, our 1974 Ambassador with center twin beds does have a 12 volt
outlet on the street side. Also has 12 volt
outlet in the bathroom and in the living room just above the credenza near the refrigerator wall/ac thermostat.
As a side note, our center galley actually only has one twin bed now, the second twin bed space became a stainless steel counter and sink. Kind of hard to sleep on but great place for coffee pots, food prep, and cooking. (smile)