I'm not up on the available options for changing out a threadless fork for a threaded one, but as a long time owner of a Bianchi Milano with 1 1/8 inch threaded steerer, I can say that the selection of 1 1/8 quill stems is limited. Most of the ones availble look a lot like typical threadless stems welded to a too-skinny quill, or something that belongs on a beach cruiser. Probably not the look you're going for if you're attracted to the aesthetic of elegant quill stems such as Cinelli or Nitto. Investigate thoroughly before embarking on this path