I didn't replace the harness, but my front lights are grounded on each side, just to the rear of the horn mounts. The factory originally used a spring clip that takes a sheet metal screw through the center and a bullet on each side (one for headlights, one for marker/turn signals). All of my original spring clips have broken and weren't available (at least then, maybe they are now), so I made up a short length of black wire with a ring terminal to go under the sheet metal screw, and a bullet on the other end to go into a 4-way sleeve along with the two wires.
In the rear, the factory relied on the ground through the mounting screws and the spring clips that they screw into. That is far from secure in my opinion, so instead I made up a black wire that daisy-chained from fixture to fixture (with a bullet at each one), then followed the harness around the side of the trunk to a ring terminal at the RH gas tank mounting bolt. The same ring terminal also has a second wire that runs up to the sender in the top of the fuel tank. I added an "internal star" lockwasher to ensure that the ring terminal made good electrical contact with the bolt head.