under drive pulleys probably aren't going to give you the power your looking for if your wanting the power f a supercharger or turbo.
but I would say, for a cheaper upgrade, headers, exhaust, Mopar performance air cleaner, heads (can get expensive).
Now if you go with the thought that "there's no replacement for displacement" then I would say the 408 stroker or 426 stroker from Hughes Performance. Hemisized!!!

 

does anyone know of anybody who has actually used the 426 stroker kit? I was thinking it about it but havent actually seen anyone with it. I dont have the money to play with some experimental. Although on the subject of turbos I do know someone who put a diesel turbo on a gas truck. It was awesome for about 50 feet. HAHA. Lets just say now he has some fresh air holes in his hood.

 

here is a 426 stroker kit i know at least 3 guys running this kit and love it...

http://www.hughesengines.com/partRes...0&pType=CK

 

i think it would be awesome. though a 426 stroker may not be the most streetable truck in the world, it would rock.

 

Superchargers are real easy to install so there is much less down time than a stroker.
Stroker does have more power potential than a blown 360 (if 360 stock) but can cost 2x as much or more.
Blown 408 or 426 both have the same max potential hp rating with the small block heads and oem block being the limiting factor.