Need a Mopar guru: 273 part-throttle ping driving me crazy!

Do this, Start it from stone cold and blast off. Either direction I leave out from my place I have to go down and more importantly up hills. Anyway...
Run the dog crap out of it and I'll betcha you cant make it ping even up hill.
The ping will begin only after it gets too hot.
I did have the very same issue and tried everything imaginable except replacing the 35 year old radiator. New radiator was the cure all along.
Take into account that the 35 year old pizz poor gauge wasn't indicating too hot either so I was clueless to the actual condition.
You might also note that my stated experience took place in late 80s when there was no internet to ask.