A crude method that could be used for interfacing future projects, as well as the current one. While only needing to interface with eleven, 4-bit circuits, it's logical to have spare and sixteen works out nicely. Use of binary 0000 - 1111 with a 74154  which "Decodes 4 Binary-Coded Inputs into One of 16 Mutually Exclusive Outputs" and jumper holes for desired circuits address, we are able to relay "electronically switch" between PCB's.

binary-interface-selector.png

For complete circuit diagram, view this binary-interface02.png link.

The BinaryInterfaceSelector.sh script, makes changing PCB's easy with a pick of 0 - 15, then displays pin values.
Wiring diagrams of input interface-bus-cable.png and output interface-bus-cable2.png cabling.