Well, wadayano... you're absolutely correct. Clocks getting power from the BAT and the light comes on when I pull the light switch. So I expect then to plug the tach light into the grey splitter, but I've got my aftermarket gauges in that for their backlight. I doubt there's much of a draw so maybe just split it again and add the tach light?
'68 400HO Coupe, 4 spd, 259 interior, Windward Blue. My other car's a Johnson 15 outboard on a '61 Starcraft rowboat... Just sayin'.