Purchased a white 1970 TDF locally 2 years ago from a collector, had been parked for years although someone had replaced most of the French components with early 1970s Japanese. I have since put mostly French parts back on though not original ones. You might want to consider a good Ideale leather saddle ( the plastic original is generally quite uncomfortable ) as well as switching to clincher 700C wheels and buying pair of Rene Herse 32mm tires. They are nice enough to make one basically forget tubulars although admittedly for now I am using 30mm Challenge tubs on my TDF.
Pictured with 25mm tubulars - I do prefer the more prominent curve on the earliest TDF forks as well as the leaf style seat stay caps along with the longer point lugs. Gitane did what they could to simplify frame construction as the bike boom went into full swing but they are still nice bikes regardless.
The last image is how it looked when I bought the bike. The only original parts left were the stem, handlebars, Stronglight headset and the various frame cable clamps.