On second thoughts, I think you might be right about the location of the dizzy. The 2CV had it behind the fan and I don't think the GS were preset, I think the dwell was set using a little Allen key through the side of the dizzy.If I remember right they went behind the big fan at the front of the engine. I also seem to remember the gap being preset.
It'll be 30 years since I did one so it's a bit vague now, sorry.