That's odd... just looked at the tires that are on the truck now, and they're not the OEM size that TireRack says it should have.
The tires on there now are "Wild Country" 265/75/16's, 123/120Q, load rating E. The spare tire is a FireStone tire in the same size... so I gotta think, 265 is the OEM size that came on the truck.