Kristijan; I finally figured out what kind of a car you are working with. I love it and think it would be a good woodgas / charcoal gas vehicle.
Back to the distributor. We DID have vacuum advances on older cars--- when you opened the throttle the vacuum in the intake manifold dropped and that vacuum drop changed the timing.
We DID have centrifugal force advance where as the speed of the distributor shaft sped up, the weights would swing out and change the timing.
NOW you have a computer that READS vacuum, and ENGINE RPM and it slows down or increases the spark. There is NO actual moving advance mechanisms in the distributor, The computer fires the spark at just the right time based on temperature, vacuum RPM and others.. Having said that, I would just go ahead and build your charcoal gasifier and wait and see what the computer does to correct for charcoal gas. You might have to do something with the MASS AIR FLOW sensor if it has one. ( not on all cars )TomC
PS Looking back at your distributor, I don't see any slotted holes that could be used to adjust the timing. I'm sort of thinking you drop that distributor in at the proper point and the computer takes it from there. Haven't ever had on like that, but that is what I think I see in the picture.