CJ,
Okay,
When you say rebuild kit for the steering box, is it the kit that has the 22 new bearings, 2 cups and shims for the worm gear shaft? Did you also get a new sector shaft kit? This is the kit that includes 2 new bushings, a seal, and a new shaft with 2 nubs that ride in the worm gear portion of the steering wheel shaft. (Out side end attaches to the pitman arm)
If so, then the sector shaft may need to be tightened a bit with the exterior adjustment screw.
If you didn't replace this portion of the gear box, take it apart and inspect the 2 nubs. This is the wear point. (The Steering shaft at the worm gear can wear also, but less) Even a 1/16" wear on the nubs can translate into a couple inches of play at the steering wheel.
Not sure why you will see frame flex. My cross over tube? (radiator sits on it) had broken where it attaches to the frame. I had to weld it. Funny thing, once I squared up the frame and welded that back in, my "jeep lean" to the driver side disappeared.
The only thing I replaced on my steering system was that sector shaft. And in degrees, 15 turned into 2.
Tim