Gents...350 SB, Edelbrock 600 CFM carb (1405), Performer Intake and Mild cam, fuelie heads, Mallory HEI.

How far can I advance the timing ...or what's maybe a rule of thumb..ie. "keep going until...".

I am running 14 deg btdc, car runs fine, though a bit rich...wondering how far can I "push" it?

For that matter, what is the realationship of "too rich" and timing?

You can advance until it pings or performance decreases. That is the big question, where is that? You need to experiment with initial advance and total and watch for pinging. When you get it were you think it is ok, run it at the strip.