I´m glad you folks like te site, but to come back to my initial question, take a second look at this picture:

http://www.museumofamericanspeed.com/Collections/Engines/600pix/IMG6654.JPG

The middle carb seems to have an own intake that is not cannected to the Offy. Looks like somebody has made 3 extra intake runners to feed each cylinder.

I wonder if they also splited the original runners.

Frank