Boxing the frame is only efficient at adding strength to the frame from vertical loads (think of a pickup with a lot of weight in the bed, you want to add vertical members at the front of the bed).
For adding strength to a frame in regards to twisting it (like when you've got 2 wheels on the ground), the most efficient way to add strength is by increasing the diameter of the structure. Ideally, you would move the two frame rails farther apart from each-other (not very practical). Instead, adding a well-designed cage that spreads the rotational loads from the original frame further out will make things a lot stronger without adding tons of unnecessary weight.
The problem with the frame at the steering box is the bending stress due to the poorly supported passenger-drivers-direction force. Adding a rigid member connecting the frame horns (such as a bumper that is loaded in compression/tension under this load), keeping the member under the radiator in good condition, a good engine crossmember, etc. are the most efficient ways to deal with that problem. The ORD brace takes that rotation of the steering box and transfers it to a compressive load across the brace to a compressive load across the member under the radiator.
You want to reduce or eliminate as much bending stress as possible by replacing it with compressive/tension. Boxing the frame at the box will help by tying the top and bottom horizontal planes together, but it is one of the least efficient ways to deal with that force. I'm not saying there's a lot of better options though. Actually, adding horizontal plane to the frame would be a lot better if it were possible to fit it...such as cutting off the top of the frame and welding in some 2x.250" strap maybe. Or maybe you could work it in to the design of some shock hoops...
Hydro assist is by far the best thing you can do to reduce stress at the steering box.
