Hi, please do either send me a picture carlbest@excite.com or post one here.
The Ball and Ball carbs on my dual setup have a vacuum line connected only to the front carb. Both carbs have idle circuits though, and both carbs also have accelerator pumps and chokes.
I don't see any reason why you couldn't configure that triple setup the way you describe if you can find some of the old carbs that were used in the tri-power setups. As for orientation of the linkages, that sounds like a fun excersize in geometry and metal fabrication.

Sure would make life easy for me if I didn't have to worry about getting the idle mixture the same on both of them!