Need help on Carburetor info

Most likely, just changing carbs will not gain much for you, unless your stock carb is very restrictive (which is possible). However, the gains you can get come into play since you'll likely have to change intake as well, and will be able to use a better flowing intake. Beyond that, basic upgrades are always headers, and then cam/valvetrain. If you don't want to get into the engine, then headers/carb/intake is a good place to start.

From the looks of it though, 4bbl intakes for the 3.8 aren't real cheap. googling gave me this provider:
http://www.moranav6racing.com/category.html?CategoryID=2