FWIW I believe their SC stage 1 kit includes all you'd need at a reasonable price. (off to check the price)
For $419 then add $18 for B'ville belt. (less core charge for PCM)
The INTENSE™ Level 1 L67/L32 Performance Package includes:
INT-FWI-xxx - INTENSE™ Fenderwell Intake Kit
IMH-340 - INTENSE™ Modular Pulley System with 3.40" Pulley - L67 equipped vehicles ONLY
IMH-360 - INTENSE™ Modular Pulley System with 3.60" Pulley - L32 equipped vehicles ONLY
GB6-660 - Goodyear Gatorback Supercharger Belt
GB6-715 - Goodyear Gatorback Supercharger Belt for Bonneville Only (+$18.00)
TST-180 - INTENSE™ High Performance 180 Degree Thermostat
ASP-605 x 6 - Autolite® 605(one heat range colder than stock) Copper Core Spark Plugs
PCM-xxxxx-xxxx - INTENSE™ Standard Powertrain Control Module
You'd get everything you need, plus a few extras. The FWI kit includes the filter.
00 Regal GS: All kinds of cool stuff.