Originally Posted by repechage

hold but add vagueness to shifting.
i think there is concern where there should not be.
measure the rear triangle width to determine 5 or 6 speed spacing. The French often made 5 Speed 122-123 instead of 120mm wide.

i think the bigger concern is the low end Simplex prestige front mechanisms on 28.6 tubes- one of the contributing factors to the nylon bodies cracking, that and age and UV exposure. I do not anticipate you looking for one of those. The frame has Campagnolo ends... let that guide you. If you want to use a French rear mech it needs to be designed for a Campagnolo end.