I had one of those back when dinosaurs still roamed the earth. I had a 5lb pulley that came with it. I cut a couple key ways in bored a bigger hole in an aluminum underdrive alternator pulley and put it on. The new pulley was half the size or less of the original. I pegged the boost gauge at 15 psi as soon as I stepped on the gas. The unfortunate part is that supercharger is so inefficient that the extra boost wasn't really doing much except pumping 15+ psi of heat into the engine.