The steering column shaft is part of the steering box. The clamp on the bottom will only allow the column housing to be be removed once the clamp at the bottom of the dash is removed, and the steering wheel and top bearing are removed. The steering shaft is hollow, be very careful not to bend it or its junk.

You either have to remove the steering box. or you have to lift the cab over the column. I checked my 54 Dodge truck service manual to be sure I wasn't leading you astray. Sorry. Gene