Picture is too dark to see the ground connection.....Just make sure your new plugs only have one wire from each one to your relay or switch....The head is grounded by being attached to the block....The old style plugs had the last or first plug by cylinder # attached to ground and then to the next plug up the string with the buss bars.....Parallel new style plugs use the housing of the plug as the 2nd conductor which is ground when they are screwed into the head.....The new plugs are all fed 12 volts from the relay or switch depending on how you wired it....I think this is what you are asking......

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1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)