As the two men worked around the car, Minore compiled a list of the small parts that were still needed for the Olds, like the downshift cable firewall plug to fill this square hole in the firewall. Since the car was equipped with a four-speed, there was no downshift cable to pass through here. A Turbo 400&ndash;equipped car would share the same firewall plug, as it has an electric downshift controlled by a switch mounted to the gas pedal mounting bracket on the inside of the firewall.