What Rich said.
1st, what's your pressure?
2nd, squat down and look at the front end components while somebody moves the steering wheel back and forth. You may be able to easily see where the slop is.
I've been chasing wander on my CJ5 for over 20 years. Different problems have caused wander over the years for me: wore out spring bushings, bad tre's, a wore-out steering box, cracked frame support that let the frame rail twist at the steering box, etc.
Has your truck ever been right with that setup (springs/swampers/etc). Gradually gotten worse over time? Suddenly went from good to bad? New to you and always been that way?