Most every time I've seen a worn out trac bar, the steering wheel was 1/8 to a 1/4 from the center position when driving in a straight line. Other things may cause this, but I look at the trac bar first.
Most times you can get somebody to push on the top fender (push near the seam so you don't dent the fender), pushing sideways and you can see and/or hear the trac bar play, whether it be the top joint, the bottom joint, or a loose bracket. I even found one with the wrong bolt in the bottom trac bar joint this way.
Also have a look at the U joint in the steering column. A couple different setups over the years, but somewhere near the steering box there is a joint in the steering column of some sort.
I put a rebuilt steering box in my 87 and 88, both around 160.000 miles */-. My 96 has well over 200,000, no issues with the steering box yet.