Consider a low-bandwidth current loop instead, with optical isolation. Then you don't need to think about any potential differences between the two sites, and the driver side will adjust the power to take into account the length of the cable, i.e. the cable resistance.

Using a scheme with differential voltages requires you to have large enough voltages that the other side will still have distinct potential differences, so whatever solution you do, normal transceiver chips will often have too low transmit voltage. And a custom transmit stage with higher voltages would produce too high voltages if you connect without that long cable.