If you don't need the steerer length then by all means cut off the threaded portion. If you need all the steerer length you can get, don't be shy about clamping on the threaded portion. I've done it. If you feel the need for reinforcement or additional strength, use Bondo or JB Weld in the threads and smooth it.


You will need the top half of a threadless headset. Your local co-op might have the pieces cheap to be used as a test setup before you spend real money on a new component, or that might just work well enough for you to live with. Star nut and cap should be available but you might need to search for them.


If you can't find the top pieces easily and are just itching to get this thing built, then go ahead and file the threads out of your top cone. I'd be concerned about some slop in the setup that the real threadless cone and centering washer would eliminate but, what the hell, go for it! Good luck!