French threaded steer tubes have a flat instead of a keyway for the no-turn washer. If you need a French headset, heres the best deal you'll find on one of the lightest and best French headsets ever made:
http://www.xxcycle.com/a9,,en.php
They're in France, but they ship fast and don't overcharge for shipping. I can get stuff faster from them than I can from Harris Cyclery.
If your bottom bracket needs to be replaced and is Swiss, it's a much bigger problem that if it's French. French is hard to find. Swiss is nearly impossible.