Threadless or threaded depends only on the fork, not on the frame. If you buy a threadless fork for your frame, you will also need a threadless headset and stem.

Threadless forks come with an longer steerer tube than almost any frame requires and you cut it to the desired length after you choose the headset, stem and any spacers you want to have the handlebars positioned to your liking.

BTW, threadless has become the de facto standard for newer bikes and threaded steerers and headsets are getting to be rare.