but before you go thru all that, WHATS YOUR COMPRESSION RATION, CAM , and HEADS? Also What did you doi to the distributor, whats the ttal timing? vacuum advance hooked up?

If you have under 10.25:1 with iron heads or slightly higher with aluminum heads, or a big nasty cam that will bleeds off some cylinder pressure, its most likely pinging because yur timing and/or distributor is messed up.