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The square bodies use multiple primary grounds, all of which are important and need to function correctly: battery-to-engine (2-gauge or the same gauge as battery-to-starter), battery-to-passenger side frame (10-gauge), battery-to-radiator support (10- or 12-gauge), engine-to-driver side frame (10-gauge), back of passenger side cylinder head-to-firewall (usually a 5/16" braided, uninsulated flat cable, although a 10-gauge insulated cable will substitute nicely), rear lamp harness-to-frame (16-gauge). Under the circumstances you've described, all of the major grounds mentioned should be disassembled, cleaned, and reassembled with some antioxidant. If any grounds are missing, add them! If there are any star washers used in the ground connections, discard them!