Use a delay flash timing light, set the speed to about 2000 RPM with the idle screw, and dial the ball back to the pointer. With the centrifugal and vacuum advance combined, the total advance will be somewhere in the neighborhood of 40 degrees at cruise RPM. The distributor housing will turn a noticeable amount when the vacuum from the carburetor comes up as speed increases.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!