Mine is off 1/4” in the drivers side and flush on the other. I checked the tire pressure and parked it in my level garage. Took a 4’ level to use as a straight edge and checked both sides. The cab on the drivers side sits 1/4” outside the bed. The passenger side is flush.
I had a long talk with a GM Body shop manager about fit and finish in cars versus trucks. He also recommended I walk the lot and look at alignment in beds, doors, hoods, etc.
I believe I will leave it alone. With a square bed and square cab there has to be a reaction to every adjusted made. I am not sure that I want a bunch of shop hands leaning and pushing on my truck to gain an 1/8” in alignment. After looking at about 10 trucks today I came to the conclusion that the bed must be slightly narrower than the cab - maybe 1/4” to 3/8”.
As long as my dogs, chickens and deer don’t know it I think I can worry about something else.
Call me crazy or lazy but I don’t think I want to deal with sales, service or body shop and be without my truck over such a minor issue.