For the initial timing 5 to 10 degrees advanced with no vacuum or mechanical would be a safe place to start and may easily be where you end up.
If you have a cam with a large overlap that results in a lot of egr going back into the cylinders at idle try running the vacuum advance on manifold vacuum. That will add ignition advance at idle and can help to improve the idle quality. Most stock builds will run the vacuum advance on ported vacuum.
