here is the link to Vince's B distributor page
http://www.fordgarage.com/pages/bdistributoradvance.htm
Initial setting with the engine not running is 19*. Note it describes the maximum advance as 36*. Given todays heads are much higher compression than the original Model B head, you probably want to avoid max advance beyond 28* if you are running a head around 5.5:1 compression. Also take into account that the origins of the springs on your advance are unknown, thus the advance curve described cannot be relied on until you verify it. If you do not have a distributor machine or a dyno, I would get a good degree scale that sits adjacent to the crank pulley and set a timing mark at 0 on the pulley. Start the engine and using a timing light, adjust the distributor so the max advance at normal running speed is at the degree you want it, for example, 28 degrees. This might mean it idles before 19 degrees. Once you get it on the road, the distributor has a small degree scale on the side that allows you to adjust the timing up or down a few degrees to suit its actual road performance.