Holy cow! Does the lock down mechanism actually move? I can probably donate a used Lamp panel board for your back box if you pay shipping.
I bought a Bally Star Trek for parts a while ago. It was sitting under an open car port in Pennsylvania for a long time. Granted it wasn't as bad as this but all of the back glass art just fell odd in chunks into the cabinet. I cleaned up some connectors and it was playing in no time. So you never know!