your blower is to small for a 540 and 20 lbs of boost, let alone you stock gm blower is not going to make 20lbs. If its a old worn gm blower that ur using expect more like 8-12lbs. any snout will work a 4" is common for most cheaper intake locations. no matter what you will be over driving 10 to 15 percent it sounds like. get 8mm pulleys