Sixpack question

Hey just doing some research for my next potential build and had some questions?
1. Are the sb and bb six pack carbs the same?

2. I can only find the oem setup of one center 350cfm and two outboard 500cfm is that what would have been on the 340?

3. With the vacuum setup as apposed to other progressive carb mechanisms do you still get the fuel economy at low ends and the power at high end and is it easily adjustable? Or do they make a progressive setup for the mopar Holley six pack?

Thanks for all your help, I have a general sense of how it is all setup just looking for experience and details.