Carb choice for high altitude?

I already know about the changes in a/f going to higher altitude, i'm planning on getting a wideband o2 sensor before i start tuning. My current carb runs great it's set up more for economy though which i want to keep; i just wanna get a holley dp and set it up for racing then i can swap the carbs back and forth depending on what i'm doing. My question really just had to do with the airflow capacity and whether that changes with altitude...