The threadless BB's use tapered split cone sleeves to wedge themselves in place. No need to bore or anything else out the threads unless you find that the rings used to wedge them are not screwing in far enough to clear the pedal cranks. And if it turns out that they aren't going in far enough just some light sanding to remove the first few thou of the crests of the old threading should give you the room needed to get the setup to bed down in good form. Google for "velo orange" and check their site to find what you need.