I have a different configuration and different idler pulley for better wrap so the standard belt sizes won't do. Imam using a gatorback 4050665 belt now on my stock pulley as well as the 3.5 which is on there now. I have a 3.3 on the shelf waiting to go on but I want to order a smaller belt to keep everything tight. I think how the gatorback numbers go is the 665=66.5".