Very timely topic. A couple of memebers in our local club have manufactured a device which can be put in the distributor to allow you to easily adjust your advance without having to weld and file the slots. One of them did a write up about it in the latest club newsletter, and it looks like an awesome idea. They state that it is Patent Pending.
I will have the opportunity to talk to both of them at our Canada Day (July 1st) show, and will find out whether they are in process, and selling them. If so, I will post up some info sometime during the weekend
Grant