That is a GREAT question! I just so happen to be able to answer it once and for all, so that anybody that searches for this answer can find it right HERE:
#K060730
You see, there have been many belt sizes mentioned when this question has been posed, and I have read anywhere from a #K060725 to a #K060735. Apparently any of these three belts will work.
However, I originally bought the #K060725, and when my UDPs were being installed, the mechanic couldn't get the belt to fit. In a last ditch effort, we had to call in a #K060730, and this belt slipped RIGHT on.
#K060730, final answer.