I got what looks like that exact same box blade with my CubCadet. It came to me, beefed up with some structure to mount a Warn 12,000 pound winch, a receiver hitch put all the way through it, and also had the end plates doubled with a layer of 3/16 diamond plate. I don't know how much use it had had, but I broke it in the same place. It was not from ripping, but from grading an old drive with lots of nasty big rocks that stuck up and would sometimes snag very hard.
To repair it, I ground V grooves and made repeated welds to reattach the broken off end. I then doubled both of the inner sides where the break had been with 2 1/2" X 1/4" angle irons, welded anywhere I could weld them, and drilled those through for the pins.
No time for a picture now, but I will get some later if you want.