What is the correct amount of vacumn advance?

Kory, getting the initial timing dialed into what the engine wants is just as important as the total mechanical timing dialed if your car is primarily street driven. If the intial is not dialed in the car will not idle smoothly, you will not have snappy throttle response off idle and it will be very difficult to dial in the carb to work well on the idle and transition circuits.

The method I suggested above using manifold vacuum as the guide to the ideal initial timing is the best approach. But most stock distributors have approxiamtey 24 degrees of advance in them so it will require either modifing the stock distributor or getting an aftermarket perfromance distributor that allows it to be easily adjusted.

For the most part if you have a cam that is truely suitable for street use then the intial will wind up at a value that won't kick back against the starter. If you have a radical cam that wants more than 20 degrees of initial and the starter kicks back then you will need to compromise or step up to one of the igntion boxes that accomodates a retard for starting.