[1QuickS]

Cams? Compression? Daily driver or hot rod, high RPM application (time-trial)?

Main venturis are first item to be selected and are based upon application & engine details. You can get excellent main circuit performance with either F26 or F3 emulsion tubes but jetting will differ depending upon which type you have.

Also, be sure your Webers are IDA or IDAP, if they are IDTP then you will have a transition issue that will be troubling. I have a modification kit to help tune that issue away without expensive modification of the progression circuit.