Polarity reversing switches were discontinued long ago. Be sure the breaker plate of the distributor is grounded, NOT the insulated terminal at the side of the housing. A separate ground wire from the housing to the block should not be necessary. The side terminal is connected to the movable arm of the points, and grounds the coil primary when the points close. If you attach the pigtail lead of an ice pick type test light to a good ground and touch the point of the tool to the side terminal of the distributor with the ignition switch turned on, it should light up with the points open, and go out when they close. If it's out all the time, you have an unintended ground between the side terminal and the points.
Jerry

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