Do I really want to attempt this? That thought was foremost on my mind as I sat at my worktable and looked at a SpecCast 400 to my right, and to my left, the Ertl Precision New Idea picker, recently removed from its A-C D-17 power source. New Idea touted the sub-frame as universal, for the most part, so I figured a tractor swap should be possible. The critical factor was the axle mounting brackets. I'd have to change the interior profile from A-C round to IH square. There'd be no going back after grinding away a lot of metal to make the mounting brackets fit.  I chucked a rotary file in my DremeI tool and metal shavings flew.   

On the D-17, the brackets were under the axle housing. Due to a height difference, they had to be on top of the 400's axles and therefore swapped left & right. I had to remove the raised fender mounts on top of the 400 axle housings. I also had to remove the PTO shield. The PTO assembly is plastic so I snapped off the part, sawed off the shield, and super glued the part in place again.  I painted the fan belt and drive chains flat black for a bit more authenticity.