sn-93 belt question

Iam a newbie to this whole thing so any help you guys can give me out there will be great I was woundering if any body has a part number or belt lenght for a sn-93 model i can get dayco or gates belts from my parts supplier but any part number will be fine it can be cross referenced also can the lower crank pulley be used with a underdrive pulley or does it have to be the stock lower crank pulley thanks for any help

It must be a stock crank pulley because the paxton unit will not usually fit inside after market under drive units.