Originally Posted by bluenote157

Get the velo bb and be done with it. You will have to get a square tapered crankset and new pedals (as your current pedals are threaded on differently on that current crank). Doing the whole japanese spindle with your existing cups seems like a pain and a fine tuning nightmare. You would have to find the proper length spindle with the proper distance between the races to hold your bearings in place.

A couple of side comments...
Is your stem an AVA stem? I think those have been deemed death stems. If you intend on replacing bars/stem, you can get a normal quill stem and sand it down so it fits the french 22mm headtube.

If your bike currently has a removable derailleur hanger, make sure you hang on to that when you get rid of your old derailleur. Modern derailleurs don't come with that piece.
Keep the Mafacs..get some new pads.
If you ever intend on finding a modern saddle for this and your current seatpost is older, you might have a problem finding one that you can mount to that post.
If you do get new bars, your existing brake levers may not slide over the bars...different diameter clamp.