[rpmerf]

Just a guess - someone replaced something in the steering a while back, the steering wheel was not lined up right, so they pulled it off and lined it up. I would jack the truck up and verify that it is going lock to lock on each side and nothing funky is going on.

The fix for this will be to adjust your tie rods, so the steering box is at the center of it's range when you are going straight down the road. Then remove the steering wheel and reinstall it so it is straight. May be hard to find where exact center is and may take a bit of trial and error. Adjust the tie rods by turning the adjustment sleeves 1 turn on each side so it pulls the right side in and pushes the left side out. You can watch the pitman arm to try and get it in the center of it's range. After you've made adjustments, count the number of turns from center (going straight down the road) to lock each way

You are messing with tie rods, so you will need to have it aligned afterwards if you want it to be right. If 'close enough' is good for you, the 1 turn each way, and a tape measure should be sufficient to get the toe close.