Get a LeJeune (531 double butted throughout) or a Gitane, same with the tubing.

French to French can still catch you with seat post diameter, usually between 26.2 to 26.6 with 26.4 pretty common. Headset cup diameters can differ too, if one is going from a Stronglight Competition to Campagnolo, reaming the frame and cutting the crown race seat are needed.

steerer threads 25 x1, quill diameter of the stem 22.0 mm.

BB threads 35 x 1 68mm wide, very typical until the later 80's.

My first guess would be a 56cm frame center to top, as measured back in the day, no bigger than a 57, no smaller than a 54.