Miscellaneous Ground Wires
The dash housing is pot metal, the cir board is screwed to the pot metal, the pot metal is screwed to the metal dash frame, the metal dash frame is bolted to the car body, the car body is bolted to a braded strap that is bolted to the engine block, the block is bolted to a cable that attaches to the negitave battery post.
You can always add an additional ground.