Instead of grinding on the nut, you might want to try a 12-point nut with the same threads(7/16-20) as it has a smaller diameter(9/16" socket size vrs 11/16")
A lot less risky than grinding on a stud nut IMO.
They even make one smaller(1/2"socket size), but thats getting awfully colse to the edge of the threads(7/16") IMO.
I've already looked into it and ordered 2ea for myself, so that I won't have to drill as large a hole in my baffle to clear it, and being a 12-point it should fill up more of the hole area to help control oil. At least thats the way I see it.
I'll still have to grind a bit on the pump body, but if I polish it enough there shouldn't be any stress risers to cause a crack IMO.
I must admit that I'm not 100% certain that the torque requirement will be the same for a 9/16" nut vrs. a 11/16" nut. I know that the stud stretch is what determines the clamping force. I also know that the face surface area friction against the washer will affect torque. If the face area is the same between the two, as well as the thread length, would the smaller diameter nut need more torque? Does the larger nut act like a wrench with a longer handle, and not need as much force to create the same stretch?
For instance if the nut had an insane width of 12 inches across the flats, but still had the same threads, and you could get a socket to fit, would it take as much force on the torque wrench to get the same stretch?
Maybe one of the engineering types will chim in? Please! Or anyone else for that matter.
PS I think grinding the stud down a little at a time and letting it cool off naturally(vrs quenching it in water) would work ok, but thats just my opinion, and I'm no pro!