I was researching flathead fords for a future project and ran across this:
http://www.halibrand.com/flathead_info.htm#GENERAL
They have newer Ford flathead castings, from French military surplus. Not cheap, but most dimensions and SAE thread sizes are preserved (no metric).
It just blew me away that they had used these up until the early 1990s, but I suppose in some applications, the flathead is more compact...
--Matt