Given that the bike is a bit on the small side for you, you might want to run a little taller stem. The go to stem for that is the Nitto technomic. It's not available in 22.0 in the US but it might well be in France. Even if you can only find it in 22.2, Nittos tend to be a shade undersized and sometimes they slip right in on a French bike. The Huret drop out should not be that much of a challenge since you are in France. Alternatively the drop out can be modded.
Early 70s bikes can make fine gravel grinders as they typically have clearance for wider tires. I'm running 700 x 35c tires on my 70s (I think it's a 73) Motobecane Grand Record and there might be clearance for 38c tire. A little lower gearing is helpful as well. I'm running 50/36 rings and a 14-28 5 speed freewheel on this bike. I built it up for riding on rough roads and gravel.
