Which Carb Gives a Balance of Power & MPG?
Check this out:
http://www.carburetor.ca/Tech/Carter/tqguide-Vaanth.html
As far as tuning, the best way to tune a carbureted (sp?) car is by a wide-band oxygen sensor put in the exhaust manifold and hooked up to a real-time A/F ratio meter. You simply drive the car, look at the meter under different throttle conditions, and swap jets and metering rods until the ratio is where it should be.
EDIT: Whoops, Rumblefish beat me to it...