What is the correct amount of vacumn advance?

Try running more advance and see if you go faster. Keep adding more until you either slow down or hear detonation. Then, hook up vacuum advance to ported vacuum. Increase or vacuum advance until you get a little light throttle ping, and then back it out until it goes away. If you want to be scientific, and really dial in your timing curve, evaluate your mechanical advance in 1000 RPM increments. Obviously this is easier with a manual transmission. A slight uphill grade helps as well.