If you keep the hubs and have new rims laced you can use your existing freewheel. All this discussion is assuming it actually is French threaded and not easily replaced. If you get new wheels you will almost certainly need a new non-French thread freewheel, and if your bike has any significant miles on it, means you will also probably need a new chain so the old chain does not skip on the new freewheel. See where we're going with this? Once you begin upgrading older bikes, especially French ones, it becomes a very slippery slope indeed. That is why some folks will advise that unless you are wedded to the idea of keeping this bike no matter what, you consider getting another/newer to ride and keep this one to tinker with or to hang on the wall and admire.


And before anyone shouts me down for this, let me tell you that I flat love old French bikes.