I have several sets of original ground strap bolts for Camaros Novas and Firebirds. These go from the subframe to the body mount support on the firewall. These are different than the other ground strap bolts as they go through thicker and heavier metal.
E headmarking
3 dots (:.) headmarking
35 per pair shipped to the lower 48 3 sets of each available (2 bolts per set)
