If it were me I'd take it to a body shop, tell them what your concerns are and they'll be able to pinpoint a frame issue if there is one.

 

Take a straight piece of steel and hold it vertical against the tire and measure to the body on both sides. Should be within an 1/8th of an inch difference. Check shocks, and bushings to see if they are wore out to cause the axle to shift. You could have good good bushing to the eye then find out you have rotted out bolts as well.

Check everything.

 

if bent a frame shop or body shop tnat has a frame machine

 

Or, take your truck to a frame/suspension shop and let them put it on the lift and check everything...all the anchors, tie-downs, springs, bolts, etc. in the suspension...front and rear. And, have a bud follow you down the road...watching your truck to see how its tracking going down the road. Does it pull either way? Does it hold a straight line? Lots of stuff can cause weird tire wear. The folks who see and deal with it every day are your best bet for sorting this out.

 

that is what i thought to but there all telling me it is do to overinflating witch i know is bs bc i cheek my tire's ever week 4 presure and they do not go over 34 psi so im going with out of line rear end my budy said it probley has somethign to do with my leaf spring pin is out of line ?