I've found most BB Mopars, especially street pump gas motors, like from 34 to 36 degrees before top dead center with the motor revved up high enough to have all the mechanical advance in
I also weld up the mechanical advance slots or adjust the ones that you can do with a wrench or screw driver, to have between 12 to 18 degrees BTDC at the idle rpm. I also change the advance spring to the lightest tension ones I have, so all the mechanical advance is all in by 1500 to 2000 RPM