What you are going to find is that a carb like 3310 which is a 780 vacuum, an 1850 which is a 600 vaccuum are both "street' carbs and are just about where you want them out of the box.
A carb like any of the double-pumpers have mechanical secondaries and are intended as "race" carbs have very heavy idles. Holley says this is for running with open headers and compensating for the header scavenging.
Those carbs will smart your eyes at idle and can only be leaned out buy enlarging the idle air bleed in the main body.
I haven't used the new Demon carbs yet (I'm playing with FI and multiple carbs like my Webers now) but I believe that some of them have changeable "air jets" on them for this purpose.
If you are serious about getting the mixture strength correct you are going to need to do this all on a dyno or install an oxygen sensor in the exhaust system that you can read the a/f ratio with in real time. That involves a computer with red and green lines on a graph on your computer.
