Carb choice for high altitude?

See I would agree with you, mostly based off the fact that carbs are rated at the volume of air that can flow through, not the mass or density which is what changes at higher elevations. However I have also read that because engines pull much less vacuum at higher altitudes a smaller carb is better to maintain the vacuum signal at the boosters. I still don't know though it makes sense either way LOL... I want to just go with the 750 but I don't want it to give me a nightmare trying to tune it to run smooth and responsive esp. off the line.