Hi Mark, what that refers to is on the older 6 volt cars, many had vacuum operated windshield wipers. The problem was that when you were accelerating or had the car running in overdrive, the engine vacuum was significantly diminished. To alleviate this, there was a second pump integrated into the fuel to provide a vacuum boost for the wipers. This is what is meant by a dual action, or dual pump. If your car is a '53 Manhattan it would have electric wipers which means it has a single action fuel pump as no vacuum in is needed for the wiper motor. A single pump is what you need.