1 run your hands over the front tyres - could have a flat spot , ive had new tyres like that too
2 cheack your free wheeling hubs not engaged - see if the drive shafts turn up to half turn when parked up , turn em by hand , if it moves around a bit thats not engaged if its solid it is and you need to look at your hub
3 tyre pressures
4 lift the front passenger side. of the ground with a jack and see if there is any wabble / play in the front passenger side wheel to the front drivers side - this will be idler or ball joint wear but wont give you true tracking.
5 when doing the tracking its important as you have 6 ball joints and idler . you set tracking then shake truck vigorously from side to side use the door for leverage too. you will find you set the tracking then cos it goes right ... when the truck is moved it goes out just because there are so many joints.
so once shaken set it again .
i give mine 3 shakes and its spot on every time
i did a thread on this problem ages ago ill try to find it