I think that a late 70's Motobecane will have Swiss BB threads and I'll bet that someone used British cups. A Phil Wood BB and Swiss rings will save it, but figure about $140. You can watch eBay for a set of Swiss cups and maybe get them for $50. Swiss bottom brackets are the rarest of them all. You can find a shop that will retap the shell to Italian size and use an Italian BB with a 2mm spacer. I have no idea what that would cost.
You have to decide if it's worth it:
http://cgi.ebay.com/Vintage-Campagno...d=p3286.c0.m14