First, double check your casting number on the existing flywheel. I'd bet the "3704832" is actually 3704837, which corresponds to an original 6v heavy duty flywheel for '42-'53 6 cylinder Passenger, and 1/2 ton heavy duty clutches and the same years for 3/4, 1 Ton and Utility sized trucks. See screenshot below.
I think you have two choices to pursue here. The 168 tooth 12v ring gear is not designed to fit the earlier 6v flywheel and to my knowledge, no one makes/offers a 168 tooth ring gear that fits the smaller 6v flywheel. You can either replace the ring gear on your existing flywheel (139 tooth) and use a 6v starter, which can be done with a 12v system as long as you don't crank on it too much, or replace your 6v flywheel with a 12v flywheel and matching 12v starter.
Hope this might offer some help to answer your question.
Edit note - Jerry got to the post button first.
