Keep in mind that the original Ford springs had leaves of variable thickness. Modern spring-makers may be able to get the same spring rate with fewer leaves of different thicknesses. For example, Detroit Eaton provides a 10-leaf front spring for Model As to replace the original 12-leaf, and an 8-leaf front spring to replace the original 10-leaf. They do provide an 8-leaf rear for coupes and a 7-leaf rear for roadsters.
If anyone has ready access to Marco Tahtaras' excellent spring chart, would you please post it?