Use the 45, we ran a 44 on one of Dan's and the wear pattern/witness marks only cover half of each belt side angle.
Edit:
Had one in our group blow a Gates carbon after 2 days of riding. Checked alignment, .110" out. All is well now.
Would this also apply to the Polaris belts on the Pro? Use 3211183 if you have the Indy Dan cut on your clutch compared to the 3211115 for stock clutches?