Kickin i did suspension for years bud, there is a few reasons, now I am leaving in a few hours to spend time with the lady, but you are welcome to call me at anytime this weekend.
first off are you a heavy person? over 250lbs,
the reason is ask , is if you are then the truck needs alignment with you in it,
no dissrespect , but over 250 it has an effect on the alignment when you are in the truck, and aligning it out of the truck will change everything.
Now pulling
tires, swap them, sometimes it has an effect.
but most of the time its caster or camber.
Caster is the relation of the upper ball joint to the lower ball joint.
now both sides should be exactly the same, if not , one tire will think its rolling faster than the other and cause pulling issues.
Camber is whether the top of the tire is leaning in or out.
now if it is leanig out on the passenger side, it can cause a pulling issue.
both sides with out tires being so wide should be around zero degrees.
actually with the drivers side out about .2 degree.
dont go by the factory settings, they are good , but onley get you close.
now honestly I made every customer sit in the car after I got the alingment close.
this way when they are in it, you can set the pasenger close to zero, and the drivers close but out jsut a tad.
tie rods do nothing for pulling, ball joints should be checked for wear, but nowwadays they usually last a very long time.
also have them maybe do a four wheel alignment, it is possible that the rear axle is cocked jsut a touch, but usually dont cause a pull
but if you ahad the specs I could do more, but it should read somehting like this
.............pass................drivers......
caster......5.5...................5.5....
camber......0.0..................0.2.....
toe in..........0....................0......
but caster and camber combinations is usually the culprit, now what you should do is find a very old man that does them and cares about his work