I've seen BBs at 103mm width being sold for SS/FG applications, so that could be a good legnth for you. 118mm was pretty common for double cranks in the 80's specially with French bikes with Stronglight or TA cranks, but 118mm must have been appropriate for non-French triples. 113mm was the typical legnths to accomodate double cranks like Shimano DA.
Chombi