[My6t5mustang]

So I am doing some work behind the instrument cluster on a 69 Firebird. This car has a working Casco style cigarette lighter but wanted to change it over to the original Rochester style.. the old casco has a power and a ground wire, where the Rochester only has a single hot wire? Where does this type of lighter ground? The cluster that it mounts to is plastic.. do you just ground the housing to a ground wire??