I also have a Ford 515 sickle mower and use it on my TC29D, which is the same tractor as your TC33D with a different engine. I got my sickle mower used, so the breakback arm was there but the pin and bracket it attaches to on the tractor was missing. Ford orginally set it up so that that pin attached to the 3pt arm itself with a clamp type bracket and that was the part I didn't have. So, I fabricated a bracket that goes on the arm. Do you have an owner's manual? If not, you can get one for less than $10 at a New Holland dealer, but it will take a week or two (they print them on order). I'm at work now, but when I get home I'll scan the page in the manual that shows it and post it here. I can also take a picture of the one that I made, but won't be able to show you how it hooks on because I can't put it on the tractor right now because of another attachment that's currently in the way.