Just adding some information. This is a direct replacement for the stock jackshaft pulley, no modifications needed (8 rib to the supercharger and 7 rib on the jackshaft to crank pulley). Just unbolt the stock pulley and bolt this one on, done in a matter of 10 minutes and reuse the stock belts. I ran this with a 10% SC pulley for a total of 20% on a ported 94 blower.