what to do with the six

Hey guys,
I have a slant six in my 73' dart swinger and by the looks of it hasn't been touched since the day it came out of the factory. It runs, but i would like to restore it to its greatest once again...or atleast get it runnin cleaner. I'm puttin new spark plugs in it tomorro and it already has a new 1bbl carb. Any opinions on where to start or what to do next? Also i wanted to get this six mean if you get what i'm saying so any ideas or thoughts on how to do that would be awesome.
Thanks, Brandon