IMHO a Weber expert in NA engines isn't going to be much help without blower experience.
Webers are designed to be run as IR: one bbl. feeds one intake port with almost no plenum volume separating the intake valve from the venturi. This is why the CFM of one bbl. is not 1/8 of the total displacement air flow.
I've never seen 4 X 2 Webers on a blower.
The vacuum signal from the GMC is completely unlike any NA engine. Important: a small blower, or one turning too slowly, will still have vacuum at light throttle. A large blower will have boost very quickly, so the power system (where that is in a Weber?) will come on at different RPM and throttle positions depending on how large vs. how fast it's driven.
I may have something on my site here:
http://victorylibrary.com/mopar/blower/blower-carb6.htm