French BB solution?
 

I came across this BB and axle source on another forum. Does anyone know if any of these axles will work with the narrow BB cups to convert a 70's Peugeot to square taper? I'm too busy right now to pull my crankset apart to measure the axle. I should have measured it and wrote it down when assembling.
Thanks, Greg

http://www.yst-corp.com.tw/new/axles_bbset01.html

I assume these are JIS taper spindles; so you should be able to find something there that works well enough, so long as you're OK with a Japanese crankset (but some of them are not JIS, such as Sugino Mighty and 75, and Suntour Sprint/Superbe, maybe Dura-Ace too).

Sheldon Brown has a page on spindle lengths, but it doesn't tell you much more than that table does. Sutherland's Manual (available online) has a lot of compatibility information, including "cup factors" that indicate how one mfgrs cups compare to another's. Another avenue might be to look out for a Sugino French-threaded BB complete on eBay; Shimano made them too, though they appear less often. A Sugino (or Suntour) MW-68 spindle or a Campagnolo 68-SS should fit an older Campagnolo crank (NR/SR), or a Sugino Mighty or Suntour Superbe, acceptably. As far as I can tell, they seem to be the same taper end size, and have roughly the same spindle length, though they do differ somewhat in the right-side length.

The spindles you will looking for are the ones that start with number 5 in that chart. They were really for a 70mm wide bottom bracket, but because old french bottom bracket cups were narrower than normal, they will work even though your peugeot has a 68mm bottom bracket shell.

That's pretty interesting but can you actually buy those anywhere? Lately I've seen some very useful parts (from a C&V perspective) advertised on manufacturers' websites, usually from Taiwan, China, or India and most likely because there are so many bikes there still in use that use older technology, but I have no idea where you could buy that stuff in the US. I'm not even sure some of that stuff is in general production - more like "here's what's available in our catalog and if you want to buy a 1000 pieces we'll whip some up for you". But who knows.