The standard belt for the 3.25” pulley is 99.5”.
3.25” x 3.14 is 10.21”, and the 2.75” pulley is 8.64”, so that is a difference of 1.56” and considering the power, a tight belt is ideal, which gives more credence to what Bill said when he suggested you go with 1.5-2” shorter. Again, that is if you have the stock belt already.
Regardless, the goal is to find a belt between 97.5-98”.
I would suggest getting a six rib belt of the Gatorback or poly-v variety, so you don’t get belt squeal. These are the types of belts included in the supercharger kits.
https://static1.squarespace.com/stat..._FA_LowRes.pdf
https://static1.squarespace.com/stat...heet_v2_HR.pdf