That is a common area for cracks. Several companies make steering box braces. Currie is one.
YJ frames are thicker, one-piece, mandrel bent rails and don't typically have this problem. CJ frames are slightly thinner, two piece channels that were welded together and the cross section narrows at the engine bay. CJ frames are fine for most peoples needs and can handle occasional abuse. Under heavy abuse, I have seen cracks at the motor mounts and welded areas.
If you do weld to it, do it slowly at the lowest viable setting and let it cool often.