[Bruce Lancaster]

That pic is from a Ford patent covering some distributor details AND a simple static timing adjustment plate (identical in concept to aftermarket 1930's pieces) that was to be welded to the firewalls of Fords as standard equipment! The electrical arrangements for that have some very clever bits.
Bulletins show 11A as having 22 degrees crank maximum versus 16 for the 68 mechanism. I think the big factor is that the 11 starts advancing at a lower RPM, right off idle, which I believe flatheads like.