Also your harrow is a Dunham Lear not a true Underferth Harrowgator. The major difference is on how they control the level/angle of the front hitch. If you look at yours there is a bracket welded to the front hitch where it pivots. Then there is a wedge shaped bracket that adjusts to let you change the angle. This system did not work very well. As you can see yours is bent like just about every other one I ever saw.
Now if you look at the picture of the Underferth Harrowgator, you will see the two adjust able angle braces that run from the hydraulic cylinder mount to the frame of the unit. These will slide inside them selves when lifted up all the way. Then when you lower the harrow they hit the stop pin that allows you to adjust the tilt/angle of the entire unit.
In ground that has trash or clumps of grass you run it with the front held up higher than the back. This will let the trash/clumps work themselves through the harrow. Then in clean worked ground you can level it out for maximum leveling.
Your first try can be reused if you find a piece of pipe/rod that will slide in the square tube you have. If you find a piece then all you need to do is cut the current one right in front of the cylinder mount. The weld the sliding piece to the front yoke you already have. Then drill a hole in the square tube to hook it to the rear lift wheel rock shaft.