Many years ago, PC's came with a parallel port that was intended to drive parallel signals to a printer. It was driven via exactly that same IC, i.e. 74LS245, and the lines were series-terminated through resistors.

Now, I don't remember what the data line resistor values were, but, clearly, this is a similar case to what you're considering. The IBM-supplied cables were not ribbon cable, but ribbons were often enough used in similar situations. The characteristic impedance of this ribbon cable was considered to be approximately 110 ohms. Just as in your case, IIRC, a single ground wire return was apparently sufficient to make the entire subsystem work.

Perhaps a look at the old, original, IBM PC printer interface would answer most of your questions.

RE