This has all the makings of a fabulous story like "Snow Whyte." I find it fascinating that each member here has slightly different advice. There simply is no one right way to proceed! My own suggestion is ask your personal lawyer or family attorney for their advice on the ownership. I think it's important always to start with someone you trust. Then follow what they say. Although I see Michael S's point about the original owner having a claim to the property, even if they abandoned it, the fact that you care about the car makes me hope you are able to take over the project yourself.
I have one small, practical question. What's the black dot to the right of the light switch in picture w113q? (BTW, perhaps you should turn the light switch to the "off" position. You don't want to drain your battery :-)
Good luck and please continue to tell your story here, in detail.