Although I haven't tried it, I don't think the timing will advance for a rich mixture. The service manual makes to reference to mixture input to the EZK, and there is no test for spark advance based on fuel mixture.

Don't trust the timing marks on the harmonic balancer. When the harmonic balancers get old, the outer ring with the timing marks slips relative to the inner hub which is indexed to the crankshaft. Pull number one spark plug and find TDC carefully using a probe in the spark plug hole. You also need to remove the top timing cover and verify that the cam is in proper time with the crankshaft. I have had three bad harmonic balancers in our fleet of cars, and I think the one on my wife's car is bad again.