My '69 conv. runs fine on 91 octane until hot days...I get ping issues on moderate to full throttle...I have 9 deg.timing and a 4 core...could my carb. be too small?

Make sure your dwell is setup properly, verify your total timing, and try a one step colder spark plug. If that doesn't help you probably need to richen your fuel mixture. An 850 Q-jet would be a better choice, but I'm guessing want to hold onto the HO carb, and are hoping to use it as long as you're keeping it.

Thanks Mike...I'll give that a try...