as to the dropouts on that particular frame: they look to be Huret (seems like that little half-moon black plastic stop is there in the slot) and the tab is low on the hanger (in the Campy fashion), so I'd bet this has a conventional THREADED RD hanger...if so, it should work with any conventional RD such as the one you pull off a Trek 560. There's a chance that the BB could be Swiss, but might even be BSC since the graphics point to a '78-'79 frame. Best to inquire with the gitaneusa.com folks about the model (oops, you have ID'd it as all-531, so could be this "Nation 1849" http://www.gitaneusa.com/images/catalog/1978_pg4.jpg) and what that threading could be.