The fork on my Trek 616 came off a French-threaded Motobecane Grand Touring; I pieced the headset together from Tange, Campy, and Stronglight parts. It's worked great so far. IMO, as long as the bearings fit the races and the nuts fit the threads, and the balls don't drop out over bumps, everything is as it should be.

OTOH, I would like to try out a Grand Cru headset and this seems like a good excuse.