Will a french crank set fit a regular square taper bottom bracket spindle?
Yes
… but … PS … you usually need a special extractor to get them back off … and likely require French pedal threading although it can be re-threaded to “standard”
Search the forums, this has been answered a few times.
In summary: Yes, but it won’t seat fully, ISO/JIS taper is the same, but ISO is slightly smaller. Buy a Campy AC-S BB, cheap & good ISO taper.
Some cranksets may work better than others, I had a Stronglight Mod.93 that didn’t seat properly on a JIS spindle.
Well it’s an old Stronglight crank set (search Stronglite) on ebay at the moment, but I reckon I’m going to be out bid on it very soon.
Thanks for the answers.