Hi, I have started planning to replace the discs and brakes on my 2002 Silverado 2500HD. In researching it appears there are two different rear brake hub hole sizes (4-5/8" and 4.82"). I called my local dealer's parts department and the guy there was zero help. He didn't have a clue there were more than one size. He said that he needed the number of the disc to get new ones and still would not know the diameter size I am looking for. Does any one know how to determine which size I have short of tearing apart the rear brakes BEFORE I have new discs in hand???? Thanks!

ps: I am looking to use after market higher performance discs so getting the number to the dealer based on what he said wouldn't help me much.