Where are you measuring to get your 1/8" toe-in reading?
Have you actually jacked the front end of the ground and put a pinch bar under the tire and checked for worn parts by moving the tire up and down?
Has a helper lightly turned the steering wheel back and forth while you were under the truck looking for movement?
It doesn't take a lot of wear to give you issues...wheel bearings, king pins, drag link & tie rod ends, spring shackles and spring pins can all be part of the problem.
Don't rule out old bias tires either...
Mike B
