Very nice glad to see you have your fuel pick up problem resolved. On to the sending unit, the green wire goes to the gauge, the ground is established via the sending unit mounted with screws to the tank, then the tank mounted to the frame.

Here is the way it works, power to the gauge, one lug, then the wire on the other lug goes to the sending unit. That in turn goes to the resistor that the float is connected to, as the float rises and falls it is acting like a light dimmer and the fuel gauge is the bulb.

I see a big washer there get rid of that just a nut and wire lug needed. You could cause a short with the washer and the fuel gauge will not want to work.

Keep this up and you will be driving around in no time, hotrodding is problem solving one problem at a time. Then all of a sudden you're riding around living large, way cool...