EL5371 driver and EL5372 receiver should do the trick? I have never done anything with data transmission over cables before. I assume I would need a driver on each of the dc/dc pcb's too? So it would go:

Master-driver --> cable --> DC/DCreceiver-driver --> cable --> DC/DCreceiver-driver --> cable --> DC/DCreceiver-driver .....

http://www.intersil.com/content/dam/...n73/fn7307.pdf