the chips aren't obviously on the same board.....on different bords but next to each other.
That may be obvious to you who made the thing, but how are we to know? Many (including me) forget to various degrees that those they communicate with start with a blank slate.

Anyhow, if they are "next to each other" i.e. 10" or less apart it may work at reasonable baud rates.

Now, were I to do this I would put a HC24x at each output and a HC14 at each input to the 2 boards. I have developed a "rule" for myself: no uC pin leaves the board directly.

Erik