This is not so much an answer to your question as it is a clue. I recall that in the early 70's I had a conversion for a SA hub that allowed you to put a multi-cog freewheel onto the hub. You then had a nine or fifteen speed bicycle with only a rear derailleur on the bike. The axle in the 3-speed hub was a bit longer. I had just enough thread on each end to bolt it into a Gitane Tour de France frame. And by the way can anyone refresh my memory as to who made that conversion kit?
Paul (aching for a ride in colo) Patzkowsky