I picked up a JD publication a few years ago that had a short article on a rig like this. As I recall the combines are built and used in India and use JD 5000 series tractors that are made in Pune, India. They just take the wheels and tires off the tractor and mount them on the bine then stick tractor way up top. I'm not sure how exactly they hooked it up to the combine to power it and I'm curious how they usually get the tractor up and down. After harvest is done you take tractor off and put it together and you have your tractor for the rest of the year. Apparently it makes the combine a lot cheaper to where poorer farmers can afford it. Seems rather ungainly to me but I suppose it beats harvesting by hand.