Joined: Sep 2008
Posts: 1,787
Likes: 350
From: Tepic, Nayarit, Mexico
Bikes: 48 Automoto, 49 Stallard, 50 Rotrax, 62 Jack Taylor, 67 Atala, 68 Lejeune, 72-74-75 Motobecanes, 73 RIH, 71 Zieleman, 74 Raleigh, 78 Windsor, 83 Messina (Villata), 84 Brazzo (Losa), 85 Davidson, 90 Diamondback, 92 Kestrel
It sounds like you want a wide-range drive-train, but your current one is composed entirely of racing components. I would just replace everything, and make it all-French (except for Japanese freewheel) since it's a French bike, and that way you can leave the dropout intact. Of course, this will take some money, but just pay it and make yourself happy and later you won't even remember how much it cost. I have been using a Simplex SX410GT wide-range derailleur for several years and it has worked great. There are also several nice vintage French wide-range cranks. TA Cyclotouriste uses the same arms as yours but with different rings. Nervar 631 and Stronglight 49 also are compatible with TA rings. Stronglight 99 is a later design with different rings. With any of these cranks, plus a wide-range derailleur, you'll have a lot of latitude on the gearing.