I have a couple of flat pieces of stock with rounded notches on the upper ends, and a hole @ the bottom for a bolt on my '45 GMC. They would be simple to make and if done right would look factory. 3/8" thick and about a foot long(I'll measure mine) Bolt would be on firewall, close to upper, outer corner. When they are laid flat, they rest on another bolt in the firewall. When they are open, they pick up the inner lip on the side panel.
