Pinging

I will buy most of what you offer except for the retarded part. PING is pre ignition. It can be octane related of course. The higher the octane the slower the burn. So you have to retard timing to fight ping. On modern engines that have ping sensors that is exactly what the computer does when the ping sensor sends it a signal. It will retard the timing until the ping sensor shuts up. Of course it could be running too lean as well, but I suspect it is too much advance. And I am not talking vacuum. I am talking mechanical. Not sure if you know this but your engine has both. The vacuum advance is only available at idle and once you get into a higher vacuum cruise mode. The instant you open the throttle to any adequate level for acceleration you lose all vacuum advance. One reason you are supposed to disconnect your vacuum advance when timing a car.

Yes I no that , I work on my 69 Darts mechanic for 25 years ... Did you no some 69 dart 340 4 speed cars only had mechanical advance units made by Unilite Co.. Mark where ur distributors n rotors set at n pull the unit out take it apart n check to see the springs are not rusted or sticking etc MR gasket makes a spring kit for them , pull plug out see if its over heated
I had similar problem I replace my dual point IGN with a Mopar ECU kit its set at 12 @ .. No more pings . Running a eddie afb 650 . the dual point rusted died long time ago.