How can i make my Duster more powerful?

I drive a 1973 plymouth duster with a slant six 225, its my daily driver so i cant go completely crazy, right now its hooked up to a 727 automatic transmission and has only a single barrel carb, i want to give it a little more power so im wondering about a 2 barrel carb or a 4 barrel carb, whats the ups and downs of both of them?