I currently have two projects for which I'll be using Stronglight 93 double cranks with a single chainring mounted to the outside position. Neither of these bikes has a BB right now.

#1) Jeunet 630 (French threaded BB) to be used with a 46t 1/8" ring and a wheel built around the SA S3X.

#2) Motobecane mixte (I'm told English BB) to be used with a 45t 3/32" ring and a 6 speed freewheel (126mm axle)

I understand that the Stronglight 93 double calls for a 118mm, ISO taper spindle. Is that symmetrical, though? My calculations are based on a symmetrical 118mm spindle.

I'm not interested in scouring eBay for two old Stronglight BBs (one in French and the other English) in the correct spindle length. I could wait forever and not find them.

So, I plan to just buy new, sealed, JIS taper bottom brackets for each bike.

I understand that a ISO tapered crank will set 3-4mm farther out on a JIS spindle. So, if I were to run these cranks as doubles I would ideally order a 115mm spindle. But, I'm going to be using only the outside ring position, so I need an even shorter spindle.

I'm not sure of the distance between the two chainrings on a double (not one handy to measure),but I'm guessing it's somewhere around 8mm. So I would then reduce the desired spindle by that amount, right?

That would seem to indicate I need approximately a 107mm spindle for each. What do you think? Am I close? Which would you order?