holly carb question

My friend has a '72 Dart with a 225 and 1 bbl Holly carb. There are two problems. One, it has a hesitation when applying gas from a dead stop, and you can't push too hard on the pedal or it will stall, and the other is the car's only getting around 10 mpg, and we know it should be better then that. It other wise runs well. The carb has been rebuilt. What adjustments, or what things can we look at to solve these problems? Thanks