I believe they all use the stock belt. If I remember correctly, you are going to swap the crank pulley and one other pulley to make up the difference in size. I believe it is the idler pulley, but I could be wrong.

I thought Erick told me that the Stage I pulley only requires the crank pulley, original belt - but the stage two requires the additional pulley to make the original belt work.

Could be wrong...but that's how I understood him.

SQ