Yep, as above, so long as you have enough unthreaded steerer you should be fine (don't clamp your stem around the threaded portion as this will be significantly weaker) but if you wanted to stay threaded then any decent bike shop should be able to thread the fork for you - I've had it done several times. Similarly I had a threaded fork with a short steerer converted to ahead by Bob Jackson, who cut and sleeved the steerer tube for me.