Well, that's the question isn't it.

The French cups are thinner walled than the Japanese cups from the same time period, so you may need a wider Italian (70mm) axle so your lock ring will have enough bite. Might not. I've done it with an English axle and had just enough threads left for the lock ring.

Then there is the crank and where it will sit on the axle. You will want to try and match the cranks and axles with the same taper, either JIS or ISO. You can mix and match but it will be a little more difficult to get a proper chainline. See here:

http://sheldonbrown.com/bbtaper.html

Check the part about "interchangeability" for a more detailed explanation.

Shin