There is no way to set the mechanical advance...it is a problem that the distributor advance weights get corroded and dont move properly so basically there is no advance at all then.
Sometimes one can take the unit apart and clean and get it working, other times a replacement is needed.
If you want vacuum advance, you can try to find a civilian distributor for the 230. These had vacuum advance and regular, car type, plugs and wires. While you lose the waterproof ability and the stock look, you do gain smoother operation and a bit better fuel mileage...though they arent the easiest things to find and you have to make sure the vacuum advance unit works as the replacement supply is all gone years ago.
Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.
Pro-choice, that's a LIE, babies don't choose to die!!