Just to update this thread, I did manage to get my box blade back into shape. I drew up some cad files to match the profile of the sides, and also a 1 1/2" wide rectangle with 3/4" half holes Long the long side. I beveled both sides and welded them in.
It took about 4 hours total, including drawing, removing rust between the moldboard and mounting plate, and getting it back off the table.
Funny part was that I took it off the table with my forklift and set it in the dirt just outside the shop, which is up a slight incline. It took several tries and a running start to get close enough with the tractor to hook it up.