Steering box repair

[Martinbuilt]

Hi.
I have a 2-tooth steering box with a damaged steering shaft. There are no threads above the steering wheel taper.
Can I use the inner column from a 7-tooth box to replace mine? I'm guessing the worm is a separate part, pressed on.
I've searched a bunch of parts catalogs, and can't figure out if those parts are interchangeable.
Thanks.