alignment

374k...Lots of turning and wear in that amount of use. So if it was me I would jack up that axle and check for kingpin wear. Look at it as you would checking ball joints on a chevy pickup. If they are worn enough they will cause a camber change that will change when you are loaded and be worse when you are empty. It will pull usually to the left but not always and the pull will feel the same as a good wind pushing you that way, it will also change the steering wheel angle when moving to resist that pull and when it's stopped you can center the wheel and the tires appear to be straight.. It will even go straight at low speed. The really strange part is that it won't show in the tire wear until it gets really bad. After that many miles and if they haven't been greasing it like they should it merits checking.

Just sayin'

 

Most trucks have the 2 piece shaft and you can straighten the steering wheel at the steering box or knuckle...
It would be best to get a 3 axle alignment and have them set the steering.
How does tire wear look?

 

Just an FYI Trucks don't have ball joints.

DO you do a proper pre-trip where you check the steering linkage?

I would say that it needs to go on the rack and have an alignment. They can check everything to make sure it is good.