Here is a link to my other post:
http://clubcobra.com/forums/showthread.php?t=97890
Something to consider is most of us are not running vacuum advance. So our cars are typically cruising down the road with the ignition retarded from optimum. This means wasted fuel, poorer throttle response and higher under hood temperatures. In a light car with a manual transmission, a SMART driver, and a start retard a good case can be made for looking out the advance.