What should my timing be set at to stop pinging at wot

There should be no vacuum at the carb at idle when you are testing the ported vacuum source. little risk of damage. Nothing like driving with pinging. It's just a question of getting it to work properly for the best performance. You solved a problem (ping), but you have sacrificed performance to do it. You tired adjusting the sitributor... How? The limits for the mechanical? Or the dashpot? You don't say where you checked the rpm points of the mechanical either. Did you just change things to see what they did, or you knew what you were doing? (not meant to sound condescending. Just looking for your thought process)