Take a look at this Carter jet and rod chart. I tried to post the charts themselves but couldn't.

http://jimsprojectgarage.weebly.com/uploads/3/0/5/7/30573187/1416930429.png

And an example tuning chart.

http://www.volvord.com/1406cal.jpg

Now that is typical of the charts for the 2 step rods. Just imagine what the tuning chart would look like for the 3 step rods. It would be about useless for most of us mere mortals. Besides, the number of pieces required to tune, which can be hard to find.

I like the CarterBrocks, but there is a reason that no aftermarket carb builder uses them. Virtually all use the Holley platform.