I have never even screwed with a supercharger before but i am thinking now is the time i need that extra boost (outran the cops but just barely, kinda scared me) But i would like to know the following- What kind of power gains will i get? What will one do to my mileage? (not that i care about mileage really, just wondering) and if i do get one does it have to be covered during the snowy or rainy days of the year? (which are many in SD)

 

There are many excellent supercharger kits out there, the purpose of your turck will depend on what SC'er is best for you.
What are you plans for this truck....towing/off road or street/strip?

 

looking for max MPH, wont be doing any towing (besides a pickup bed full of cases of Bud light every now and then) i just want something to make my pickup fast as hell.

 

Good choice...you'll be supporting my employment with Anheuser-Busch then.

As far as superchargers, a Vortech or Pro Charger will work great, but a Paxton Novi 2000 will move a little more air. On a stock shortblock, the Vortech or Pro Charger will make plenty of power.....I would recommend an intercooler for anything more than 9-10psi. If you go with a GT-40 upper and lower then you can use some of the custom kits they make for the GEN 1 Lightnings...they look something like this....

 

What will it do to my mileage and what kind of HP gains can i expect?

 

Your milage will depend on your driving habits. Under normal driving conditions your it'll be the same...WOT will use more gas than normal though.

7-8psi can give you roughly 100hp on a stock engine.

 

what about the superchargers with the chrome 3 barrels out the top of the hood? How big are they, what kind of horsepower? And do they need to be covered when it rains or snows?