They are on average 30-40 years newer and the likelyhood of getting a bood block are much higher. Casting quality is better with less core shift and supposedly higher nickel content. Blocks have the older style 59A shape with bellhousing, but have the later 8BA decks for better water flow. Here is some info on them: http://flatheaddrag.com/french.html
The exhaust smells of croissant, and when you park it next to an american flathead, it acts all snooty. The american flathead with then make a WWII we-saved-your-ass comment.
Here you go: http://www.verntardel.com/collections/french-flathead-parts/products/new-french-flathead-block
As said, better overall quality, higher nickel content. The casting as much better, the finish is smoother. When you start working on it, you will see the difference right away If you buy one, you might want to change the cam, lifters and valves! In some of them, you must do a porting job, but that's the fun job! It comes with an aluminum cast oil pan, and alu, timing cover. ............................ Taildragger&fenderless
there's 2 differents sizes in french flathead a 239ci and a 255ci, boths are from an army little truck, so take care from the flywheell it's heavier than a passenger car engine. the 255ci is a 4" stroker, it's a very good block, but you'll need to change the oil pan, the distributor, and the manifold, don't forget the porting for better flow. here's a good link from my friend peter http://www.rods-customs.com/forum/viewtopic.php?f=7&t=34 sorry it's not translated, but pix can talk. the same things, with a blower http://www.rods-customs.com/forum/viewtopic.php?f=7&t=5557 hope you will find what you need to know about the french flats
Strange..but translated ;-) http://www.microsofttranslator.com/...ds-customs.com/forum/viewtopic.php?f=7&t=5557