You can, but it will cost a significant amount of money.
You will need a new 1" threadless headset, 1" threadless fork, and 1" threadless stem. You will probably need new handlebars too.
You will also need a shop to take out your old headset and put the new one in, unless you want to spend even more money buying tools or makeshift tools.
Why do you want to do this?
Originally Posted by
ogbigbird
You could get a killer new threaded headset for half of what you'd spend to get everything to change your bike over.
You actually can't. The new headset will not fit an old Peugeot, because it will be French threaded, thus having a different dimensions on the threading.