We ended up putting 5 different carbs on the motor, and all were briefly tested for part throttle operation.
At a variety of low loads(35-80-ish hp), at a variety of rpm's(2200-3200), looking at A/F ratios being displayed from the flow turbines and a Daytona Sensors wide band showed that none of the 5 had what either of us considered "acceptable" part throttle operation...... with the best of them being in the low-12's, and some in the 11.0-11.2 range.
They worked perfectly well to use on a "race car", but wouldn't be the hot ticket on the street(in their current configuration).

I can't believe I'm going to say this........but........this is an example of a good argument for EFI.