The first step is to make sure everything is operating correctly. That means the mechanical and vacume advance are working properly. I would like to point out that I don't always practice what I preach and have put the cart before the horse:

I had a timing issue that I had dinked around with for a bit before I discovered half of the problem. The internal part of the hei shaft, the part that twists to advance the timing was seized up. Long after the problem, I have heard here on the board that the seized shaft is a common problem with hei distributors. I don't know the year of my hei because it was a freebee bone lying around, but I belive it is about the same vintage as your distributor.