Hi Kelly,
Firstly, welcome to the forum and many thanks for the worthy information. Also for those pictures of your set-up.
I often wondered about these carbs since I read the Hot Rod reports in the Musclecar series a while ago, hence the purchase. I checked the part numbers after my last post here and found the "B" so you are spot on with your observations regarding cfm. At the time I discovered this, I did consider the possibility of engineering in some smaller venturis (who knows?).
I have always had the idea to cast an IR manifold for a pair of these carbs to go with Canfield heads (Windsor) on a spare block of mine. The idea came from my dis-satisfaction with a 4X2 throttle body set-up which I built on a Cobra manifold a few years back. I made patterns from this manifold then but these require copying and modifying for the Autolite bore centres.
The Cross Boss plenum can go to the back of the shelf as I have no need for it presently. It's a case of too many projects and too little time, twixt ambition.