I have these on a few bikes, mostly French ones from the 40s and 50s. They look neat and shift well, although the long reach down does take some getting used to. My favorite is the Simplex Competition, as it shifts the best and has the widest range of adjustment. I have found that the Huret sometimes won't have quite enough cage travel. Most of these rod shifters were made to fit a 28.0 (French) seat tube, so there should be no problem on a 70s French bike. You also want to make sure that the cage extends down far enough to handle your small chainring. I typically run something like 32-46 on the front of these bikes, and the Simplex can handle this fine. These shifters are fairly readily available on ebay.fr, but they aren't cheap and the shipping is expensive too. Sometimes a bargain can be found if you are patient.
Early 50s Metropole racer. The band and the knob were both missing so I made new ones out of aluminum:
Early 50s Blondin racer. This Simplex shifter was actually made in Italy:
Late 40s Alleluia 650B randoneuse with original Huret shifter. The location of the brazed-on mounting bracket is not ideal for this small of an outer ring. A chainguard can be fitted to the threaded hole in the pivot pin:
Late 40s LeGreves racer, although the shifer is from the late 50s (with the plastic knob):
