I just read your post after being away from computer for a couple weeks. I looked at my 4240 literature. The older piece of SALES literature shows a smaller 4 bolt tail wheel (12" maybe). The set up and operators manual shows the larger rim and tire. My old 4240 has the smaller rim on it. As far as I can tell the early units with the CAST tailwheel lift lever had the small rim/tire, and the later plows with the fabricated weldment lever had the larger set up.