Here`s another scenario;
1) Start with good gas , 91 octane at least if you`re over 9.5-1 cr
2) Disconnect vacuum hose and plug it
3) Measure 2 and 1/8" over from the mark on your harmonic balance and make a clear mark
4) Start the engine and bring it up to 3000 rpm
5) Time the engine so the mark you made on the balancer is at the 0 mark on your timing cover.
6) Return the engine to idle and reconnect your vacuum line. You should have a total timing of 34* without any vacuum in.
7) If the engine runs fine without spark knock you can try to go back to 89 octane. If it pings again stick with the better fuel.
You might check your timing light along a known good one, I have one that`s out 13*.Best of luck
