I don't see why not? Thicknet used to be the standard!

http://en.wikipedia.org/wiki/10BASE5

http://en.wikipedia.org/wiki/Ethernet_over_coax

Some compatible cards even carry the connector onboard so no hack required. However would need a hub of some sort that was equipped with BNC connectors.

http://www.ebay.com/itm/Apple-Macintosh-Asante-MacCon-i-NB-10T-10Base-T-Thicknet-NuBus-Working-/250998814144