Running Rich

Hello All
Got the Dart back together, and started to drive around a bit. I noticed bad pinging when I would punch the pedal, and it is very rich, to the point I get a headache.
440 engine purple cam. 750 holley (brand new) new plugs
Another member on this board will let me borrow his timing light, as mine is broken.
What should I be looking for in degrees of timing, and what else should I be looking for to lean it out
thank you
George