Jack the truck up.
Grab the wearing tire top and bottom.
Push on the bottom and then on the top. If there is movement the wheel bearings are shot, aka, unit bearing, wheel hub.
If movement is minimal you will need to use a pry bar and put pressure on the knuckle and pull it away from the truck if there is movement then the upper ball joint is shot.
The ball joints and wheel bearings play a major roll in negative camber. There is no adjustment from the factory for it. You can buy alignment cams for the upper control arm, but thats a band aid.
FWIW, I rebuilt the front end of my truck around 115k. 2 new wheel bearings all the ball joints and outer tie rod ends. I wish I would have pressed new bushings into the arms as they were squeaking after all that work.
For wheel bearings I went ford out of Texas.
Bob Utter Genuine Ford Parts www.bobutterfordparts.com
Ball joints and tie rod ends I went with Moog from Rockauto.
You can buy everything from rockauto. If you want you can search the auto parts stores. Autozone oreilys and the such.
RockAuto Auto Parts
If you search the web for "rockauto discount code" you can find one that will give 5% off. Kinda helps on the big purchases. Basically it gives you free shipping most of the time.
99 x-cab 4x4 4.0l auto
mods, cranked t-bars, silencer delete, k&n drop in, Rebuilt trans ,Trans Go stage 3 shift kit, 3200stall Fuddle Racing Torque Converter,
VANIR 63mm TB, Roush split rear exit exhuast, E-Fan, JBA Headers
Auto up/down both windows, OHC, EATC (soon to be modded)
03 Crown Victoria Police Interceptor