Some MSD coils are packaged with a ground wire that jumps around the rubber mounts to ground the coil body. What is the function of that ground wire?

In the past Larry we have added an extra ground from the coil to the block.no difference in our case

Its to ground the coil. LOL. Seriously though, you don't need to run the black wire from the MSD box to the coil. You only need the orange (or whatever color). Internally the black wire in the MSD is tied to the ground wire of the MSD. As long as the neg side of the coil is grounded well you are fine.