My 04 has the 17in wheel sticker inside the door and my truck has the 20's and it did come from the factory with the 20's I think there was a recall for that. When I ordered new center caps they ran the vin and it is supposed to have the 20's.

 

Well, that's kind odd. Something I could do I guess is take my parent's gps, and see how fast that thing says that my truck is going. I don't care what my computer is set to for rims, so long as it is correct. But my truck seems to go the same speed as everyone else. I also passed up a sheriff on interstate who was radaring the lanes going a little over 70 on the speedo. So it should be right on.