I've used that hole ground to bare steel on both sides and another same size cable to one of the trunk latch bolts ground to bare steel also as well as two #4 wire block to frame grounds up front
I used one of the threaded holes by the starter in the frame and the bottom lower 7/16 bolt through the block to the tranny case and one from a 7/16 engine mount bolt on the block down to one of the k frame engine mount bolts on the passenger side, clean all the surfaces to bare metal first