I would first change/clean the points, check for worn contact area on points where they contact the distributor cam, and set the gap at .018 inch, then follow Joe's excellent advice. I ran around in circles with a similar problem as yours and couldn't get rid of the ping without losing most of my horsepower. Turned out to be badly worn points where the plastic rides on the distributor cam.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission