We bought #13 built in 1971. It is used for cabbage that is going to a sauerkraut plant for immediate processing. Ours was mounted on an 826hydro ( gold demonstrater ) that we bought just for this use. Think of the harvester being on blocks and then you back into it with the 8” channel over the top of the rear axle. We would take the forklift and pick up the tractor’s front axle until the holes line up witha block that is mounted midsection of the tractor. 2 1” bolts are installed on each side and then we drop the front axle off of the tractor. Ours was built with it’s own front axle so we just had to put our front tires on it and set the tractor’s axle aside. There was a pto mounted hydraulic pump that ran the header that brought the whole plant up to a spinning disk to cut the head off of the stump, the cleaning bed with spiral shafts to take loose leaves off and then the elevator to carry the heads up and into a truck or when it was wet to a dump cart. The 2 sets of outlets ran the header up and down, the end of the elevator reaching into the truck and the steering. Long rods ran from the tractor to the operators platform to connect the hydro,speed range and the throttle. Also brake lines were ran the length. We could change this overi in about 3 hours. We had 18.4x34 tires with duals and it would go thru anything. This worked great. On later models they used unisystems as a power source. And to top it off they used ih red for the main frame and white for the elevator.