You should be better than 10-14 in a 2wd on the highway. In town, no. But on highway I would expect closer to 17 @ 63-67 mph

That carb should be a Holley 2280. I always had problems with the choke linkage sticking/maladjusted and vacuum leaks at the throttle shafts. Definitely get the vacuum advance sorted out, that will help mpg on the highway.