Do what i did, first take a set of alligator clips and attach a set to the back of the instument pod then one to the body of the car. This should ground the cluster then try the lights. If the gauge stays ,then its a ground. You can then try to find the bad ground area or just make your own one up. Some times the ground bar could be missing if you had the dash apart at one time....
69 RA III T/A Auto 69 Sprint vert 3speed ( sold to a new home) 69 350 coupe ( new home in Denver) 69 350 HO 4spd