Charging system gremlin

Time to show my ignorance. When I bought the 67 Barracuda, it did not run and there was a number of sketchy and incomplete things. The alt was not wired up with the wiring harness. No VR. I am waiting on a new VR to replace one that does not appear to be working.

Meanwhile, the photo below shows the back of the new alt. The wiring harness connects to the bayonet (wire to VR). The alt does not have a second bayonet (that would need to be grounded), but you can see the screw attached to to something there.

Do I need to make a ground wire and attach that to ground?

Like I said, time to show my ignorance IMG_0112.jpeg