yeah timing chain was installed ok.....i had the overheating problem also just before i changed it....i just re-adjusted the valves today and going to switch the rubber fuel hose over to stainless steel braided hose to maybe help keep some of the heat out. thanks for the ideas!
The reason I ask, is that if you are getting pinging under light load, it could be the vacuum advance needs adjustment, or it is connected to the wrong vacuum source.
If not I'd suggest you graph your advance, and like D. Hearne said check to insure your timing is not coming in too quickly.
That pinging will definitely cause overheating. In fact if not taken care of it will eventually cause piston failure.