This indicates some electrical problem to me. Check block to body grounding, and CLUSTER TO BODY grounding. That is a known problem. The cluster is (poorly, OEM) grounded via the cluster mounting screws. Attach a ground pigtail to a ground point on the board, and bolt that to the column support.
One good way of insuring the block-to-body ground is good is to use a short "starter" cable, that is, eyelet to eyelet, bolted to the rear of the driver side head, and bolted to the firewall, or master cylinder mounting stud.
