forget about the mileage and put your foot in it!! Do you really expect to brag to your buddies that you get xx mpg??
I gave up a long time ago....it didn't matter if I had stock exhaust, intake and carb....... or aftermarket headers, cam, intake and carb (Holley or Edelbroc), I always got about 14 mpg around town, and 16 on the highway. It never really mattered if I drove it like it had an egg under the pedal, or if I tried to keep it pegged to the firewall.....14-16. Always.
OK, maybe the extremes were more like 13-17, but it was always about the same. This comes from years....YEARS of driving old Stangs. It never really made much difference to me if it was a stick or an auto tranny either. The best mpg I ever got with a carb (daily driving---not on a trip) was probably 17-18, but that was with the 5 speed.
Even now I get around 20, but that's with fuel injection and a 5 speed. Sorry, I'm rambling on. My best advice for good mileage is keep it tuned up, and install a vacuum gauge (it sounds like you already have one). Try to keep the vacuum above 10" or so when driving, this will keep the power valve closed, and keep you from wasting precious fuel.
Of course try hard to stay above that 5" mark to keep the secondaries shut....you know the big drain on the tank that goes along with it. Of course, opening up the secondaries is the best thing about having a carb.
