Originally Posted by vobopl
I have two forks for my bike - threadless chrome you coud see in the pics (FGG #2402) I have posted many times, and a threaded track fork. The lower race, top nut and cone of the threaded one fit the bits staying on the frame.
I would be kinda careful swapping headset bits around, they tend to be just differenet enough in very tiny ways to make things difficult. You can absolutely use the whole lower assembly of a threadless headset on a threaded bike, you just need to get an appropriately matching/threaded upper assembly.