Number of Teeth on Starter 2003 Yukon 5.3L

[wydahogal]

Hi Guys - I need a new starter for my 2003 GMC Yukon SLT 5.3L. I bought one at the local parts house and it has 9 teeth in it. I can find a better priced one online but they are asking if it is 9 teeth or 11 teeth. I called the dealer and he said it doesn't tell him on the parts list and that he only shows one starter that fits my truck. Do any of you guys know if my truck needs a 9 tooth or 11 tooth starter? Do I have to just pull the old one first? Thanks!