At the end of the 80s, at 13 I learned to use the 4000 line, and 7400, they are beautiful memories.
Here I leave an implementation XOD of the line 405xB, generic type, can multiplex different types of data. cesars/405xb
As in those circuits it was recommended to place the input at a level, for stabilization, low or high according to the consumption or to leave the output at low.
In this case, being generic, the unused input pins must have an associated data type.