I had one of these that was converted to a fix. My findings are as follows:

Any 22.2 diameter quill stem will work as long as you wrap sandpaper around it and give it a good ring for 5 minutes. It will bring it down to 22mm which is the size of your headtube/headset. After you do this, you aren't limited to the type of bars as you can use pretty much any modern bar.

VeloOrange.com sells a french threaded bb. It gives you a square tapered so you should be able to find some decent cranks and not have to deal with the french threading on the pedals.
There are other things you can do like keep the current cups and get a JIS spindle but that is way more complicated than it needs to be because you will need the right spindle that butts up the bearings properly.

I didnt have to change out my headset, but I can imagine that this will be a pain as well.

Pretty much once you take care of the bb/crank/pedals, everything else is easy.