I sure can't ID it from those 2 pics, (and it doesn't look like either Gitane I have owned) but if the seller went to the trouble of putting "Gitane" on the headtube after the respray, it probably is one. Afterall, if he wanted to produce a fake he'd likely put Colnago or Cinelli decals on it...that's what fakes around here feature. If you get a close look at it, perhaps something in this website would help you identify it:
http://www.gitaneusa.com/catalogues02.asp
Stephan has catalogues and pics from several decades, and he's usually helpful about answering questions. FWIW, $400 is a bit steep for a Gitane (even with 531 frame) with home paint job and replacement 105 components (maybe not in Norway, but in my 'hood), I'd keep hunting for a better one or a better price.