Pinging

I need some help from my FABO friends regarding fine tuning the Duster 340. I decided to try optimize the tune on my car today. The 340 is a stock rebuild with a Lunati Voodoo cam, AVS carb, factory intake and exhaust manifolds. Ignition is a Prestolite dual point converted to a Pertronix.
I unplugged the vacuum advance and got the RPM's up 3500 and set total advance to 35. I then adjusted curb idle to approx. 900 RPM with the idle solenoid stop as per the shop manual. Timing at idle was 5 DBTDC.
Carb mixture screws were adjusted using a vacuum gauge to maximize idle vacuum. Distributor clamp was tightened and vacuum line attached. The car sounds great at idle but not so good going around the block. Pings a lot with part throttle and up hill. I thought that I should be able to adjust the advance preload on the Prestolite, but Allen wrenches don't seem to engage anything when I attempted to rotate counterclockwise.
Any suggestions?