There's a mention of them in The Chevelle SS Restoration Guide. Text only, it reads:
A rare and unique option for 1970 only was RPO CD3 Electrotip wipers. These were activated by a small button on the signal lever, part number 3873684. The wires were routed down the steering column. A black cover, part number 7806271, protected wires on the column. Three extra holes were drilled in the firewall. A single 0.75 hole was drilled to the top left of the fuse panel where the harness assembly, part number 8901518, was routed through a rubber grommet that was used for protection. Two smaller, 0.147 diameter holes were drilled into the firewall next to the windshield wiper motor assembly to support the relay switch, part number 3973683.