I also added a 1.125 inch sway bar a week after the steering box. I like it a lot too. I just wish I had added a rear bar too. the *** end is a sloppy pig now, but the front sticks

 

Leaf spring cars have goofy suspension balance because of how leaf springs work. Rear sway bars help a bit, but leaf springs have inherently high roll stiffness anyway, so it doesn't make a huge difference. you just need a really good suspension setup with good springs and shocks (but most people aren't willing to spend the money).

Bump steer has nothing to do with the steering box, it has to do with the angles of the steering linkage relative to the lca's. When you start changing suspension stuff, ride height etc you can get bump steer. It's something that has to be tuned out of the suspension setup.