Has anyone ever seen a pair of holleys set up back to back (i'e with the secondary fuel bowls towards each other)? I'm trying to imagine a linkage for the throttles in an as yet fantasy induction system. I believe some of the crossram intakes on early z28s had this set up, but all the pictures I can find have both carbs facing forward.

And advice appreciated

Most 2x4 set ups are either both facing forward, or both sideways. To do what your wanting would be a bear. You would have throttle linkage on opposite sides of the motor and working in opposite directions. Guss I think your asking for MAJOR headaches trying to make something like that work.