I just wanted to address this comment with more detail. When I worked with Wegner ordering the kit, they took into account the displacement of my engine to pick the pulleys. I currently have a 3.7" and a 3.225" pulley, they said it would make about 7psi on the big pulley (it makes over 8) and 18psi on the small pulley (it made 16.4 on the dyno). That's spinning the blower 14% faster with the small pulley. They also sell a 4" and a 3" pulley. The 3" would be 23% faster, I may order that if it will get here in time.
I looked at the 3.8L blower (it's a direct bolt in swap on this kit), but decided not to go that way because it can't use the 4" pulley, 3.7 is as big as you can go. With the 3.7" pulley you're pushing 1000hp worth of air, I don't think you want that for a driver, especially if you don't have easy access to e85. That's why I went with the 3L.