the most important thing is not to have knock at full load, not the regularity of idling.
For this is what George recommends:
Set the ignition timing to the following spec: 16 ° to 18 ° initial advance; 20 ° centrifugal advance fully in between 2800 to 3200 rpm; this equates to between 36 ° and 38 ° total advance. Street engines (operated at partial throttle) should have 10 ° vacuum advance connected to ported vacuum. In spite of what you may have read elsewhere, a combustion chamber of fixed design (Cleveland factory), used with a piston dome of fixed design (flat top), with a similar dynamic compression ratio (8.0 or less), and with a fuel of fixed octane (91 US / Canada), shall require the same ignition calibration.
The idling advance will be ............... what it will be based on your distributor and you will adjust your idle with the carburetor
The value of the maximum advance can vary depending on the dynamic ratio, how much do you have?