As for tire size. I have two 1971 Gitane bikes - one TDF and one SC - that are running 650B tires. The 42mm tires will fit. You'll need long reach Tektro brakes.
I have another 1971 Super Corsa that is running 700c rims with 32mm tires (no fenders). Each of these bikes rides like a dream.
__________________
1959 Hilton Wrigley Connoisseur (my favorite!)
1963 Hetchins Mountain King
1971 Gitane Tour de France (original owner)
* 1971 Gitane Super Corsa (crashed)
* rebuilt as upright cruiser
1971 Gitane Super Corsa #2 (sweet replacement)
1980 Ritchey Road Touring (The Grail Bike)
1982 Tom Ritchey Everest
(replacing stolen 1981 TR Everest custom)
1982 Tom Ritchey McKinley (touring pickup truck)
1985 ALAN Record (Glued & Screwed. A gift.)