I would have to check the books to see, BUT there is a lot more to this job then just bolting in a different coil ring it has to be set up to work right. It would be a waste of time to do this job an used old ring that the covering is coming off or rotted. Which ring and how thick are your magnets?
The field coil will bolt right in. What red says is true, Ford used various sized magnets (different thickness) to maintain the proper gap with the field coil. So you will need everything from the same era in order to have a magneto that fits and works.