Very nice job. I've got the same tractor and would like to do this to it too. Did you make the all the parts or order some of them? If you ordered them, where did you get them?
Another hitch mod that worked for me and would recommend:
At the end of the summer I bent one of my lift arms and some of the linkage because I didn't have the turnbuckles tight and I was trying to pry out a small dead stump with the back blade (real cause). Anyway when I removed the hitch I cut 2.25" out of the solid lift link (the one the lifts the left arm), machined a sleeve to fit over the lift link rod, slid it on one end of the rod, welded the two halves back together, slid the sleeve over the weld and then welded the ends of the sleeve in place to further reinforce the rod. Now I can pick the back blade up two feet in the air, before it would drag or catch if went up a hill. I'm also not dragging my yanmar tiller here and there across the yard. It's much nicer for plowing snow since you can lift it up fairly high.