Where does the tail lights ground on a 73 charger

[Gargemel78]

I'm putting all the wiring back into my 73 charger and I have power to all the sockets but nothing comes on, I know it's a ground issue I introduced a ground to the edge of the light bulb sockets and the tail lights came on. There's a ground pigtail at the running light not sure if it's the only one. But it doesn't do anything when grounded. My question is how do the bulbs ground? Do they ground through the fixtures ? Or is there a wire that connects and grounds them all? The wiring diagram shows it grounded at the plug but the housing is made out of plastic so cant see how that grounds

 

[miller]

Wiring diagram will show you, if there's a ground 'wire', to the bulb sockets...guessing yes.

 

[Nacho-RT74]

Driver side tail light gets a ground gray wire with an eyelet terminal what attachs to the driver side trunk rear panel reinforcement, close to sidemarket. I don't know how to call that piece. You should be find a nut inserted there.

This ground wire feeds both tail lights and sidemarkers