Should you choose to go with it as a beater frameset, here is an example of how that can turn out. Beware that what you think will be a beater may wind up at the top of your personal bike hierarchy! My '71 jostles for the top spot next to my beloved full custom Mercian, and the Mercian feels like home when I'm in its saddle.
The only stock item left on this bike is most of the stock P3 headset - a previous owner fitted it with a Zeus locknut. Phil Wood BB with French rings, Stronglight 93 (from a different Gitane!) modified for single chainring use, Kogswell sealed-bearing fixed/fixed hubset with MA3s, SR seatpost, B17, Nitto Technomic Deluxe stem with Nitto bars, old Dia-Compe aero levers (with the uber-cool electrical tape repair to a damaged hood!), MKS Sylvan pedals, Weinmann Carrera sidepulls, all on 28 mm Paselas. This was meant to be a beater bike to take on family vacations and it became my primary early morning Dawn Patrol choice. There is just something about this bike, some perfect blend of frame geometry and metric gauge 531 that simply WORKS. It's nimble AND stable, at the same time, when you punch it, it MOVES, and it's still comfortable on longer rides.
The beauty of having the ref. 881 dropouts (thanks for catalog pic, Chas.!) is that you can use ANY derailleur you want, should you choose to go that route. Total freedom! I think Stronglight cranks rule, you'll probably want Mafac Competitions rather than Racers, I would steer you towards Nitto bars and stems, and I have come to love Sun rims after building up wheelsets on both CR-18s and M13IIs.