Torque belt question

Ive measured everything on both my bikes. Both have 6 inch pulleys My MTD is 8 3/4 center to center and my Sportstyl is 8 5/8 center to center . My question is should I use a 20 series??? And if I use a 40 series what will the difference be??? Thanks
i Am pretty sure 40 series only run 1” so you would have to use a 44 series driver Which can be 3/4” with a 40 series driven. The problem is they are so heavy that when you take off there isn’t the quick snap on take off. More of a slower increase because of the spinning mass. If you are only talking about using a different belt you have to use what goes with what you have.