Sorry, I cannot even guess to estimate what may or may not be there, but also hidden. Sorry to say but your going to have to decide after a complete teardown (so far that is bringing up new challenges as you go along) what to do. A few very experienced members are advising you, and I would give that advice serious in depth consideration, and stick with that decision. I believe going against the odds can reap rewards BUT unless you thoroughly consider the entire evidence after a complete inspection, your going to have to take either a leap of faith or write it off as a parts car. I wish you the best either way, I would not even start that project, as I do not have the time or $'s to get it right. Good luck, either way!