He wants to go with a 2.2" pulley?!?! I would recommend against it. Even if he upgraded to an 8-rib pulley set up, he'd still have all kinds of belt traction problems.
If he wants to run that much boost, he'd be better off upsizing the crank pulley to speed the blower up. That way, he'll reach his desired blower RPM and get none of the annoying belt slip associated with small blower pulleys.