Other box is a factor reverb unit that mounts in the trunk.I did some checking on Ebay and it sounds like it's the same unit used from 68-70.
I'm thinking the faceplates may be different between those years though, but it's just a guess.
As far as restoring it - there must be someone out there that restores them, I would do an online search and see what you come up with.
You might be shocked at what they charge though!
And if all else fails I see working units come up on ebay quite often in the 100-250 dollar range for the radio.
The speakers should be easy enough to replace and your grills can obviously be re-painted.
I'm not sure what the other box is with the harness attached to it but if it's a main component of the system then hopefully it will still work or can be repaired or replaced.
Good luck!