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

my /6 :
9 to 1 pistons (mopar)
3 angle valve job
gasket match the head
clifford headers
comp cams 440 lift
shaved head .100
clifford 4 barrel manifold
390 carb
roller timing chain set
440 starter
melling hi-vol. Oil pump
haven't started it yet , the car isn't ready . Hope this gives you some ideas.