can you change to smaller bearings in the supercharger to get more psi's of boost?

The bearings wont change the rpm, but a smaller pulley will. You have to be careful with this because you can over boost your engine. The following is my post to another similar question. The stock pulley on a GTP's supercharger, which is an Eaton Model 90, measures 3.8 inches in diameter. This turns the supercharger 1.84 times the speed of the crankshaft, . This rotation of the supercharger pulley drives two impellers that compress the air and force it into the lower intake manifold as compressed air. If a smaller than 3.8 inch pulley (stock) is used, you increase the rpm thus increases the compression of the air inside your supercharger, called boost. Your stock pulley will translate into a maximum of about 7.5 to 8 (psi) of boost, whereas a 3.5" pulley will increase that to over 11 psi of boost. In terms of power output you can expect around 30 more horsepower and at least the same increase in torque. Caution though, turning the supercharger at higher rates can damage engine and drivetrain.