Add a suitable self tapper to form a ground with the cluster body.
Looks like a #8 sheetmetal screw works. I have some with a 1/4" hex head like others in the cluster. I can't see it hurting anything, if nothing was there before.
Got the bulbs out of the AC panel and fuel/voltage cluster. Those bulb holders are a pull out, not twist. Just to help others with similar a question.