4x4 steering issue - won't return to center

[GMC-YA68]

I didn't adjust the box on either gear box I bought from RedHead. RedHead told me with their boxes being brand new it would cause damage to them.

I have never touched the front u-joints. They are what was in it when I bought it a year ago. However it drove ok (nothing like this) when I first bought it.

I will say when I am going down the highway at 55ish and let off the skinny pedal, the truck wonders all over the road. You guys think I could put a sway bay on it?

Still going to get an alignment check. My rear is a bit higher than the front probably due to new leaf springs so I also wonder if it is causing too much force on the front axle?? Just rambling/ thinking out loud...