Probably a long shot, but does Marti have databases on all yellow Bosses made and how many are still around? Any chance finding that elusive number if it hasn't been ground also and doing an anonymous check for theft or if possible? Does this seem to be a Frankenstein car with all different date codes everywhere, if not you might be able to narrow down the build date to a window. I would try to inventory what is original to the car and what has been replaced I think this last owner knows more since it wasn't used on the street. Can you find out the last time the green car was registered and do a previous history search? Might be telling. Does the last owner of the yellow car have a public record you can research? I'm guessing you have a real Boss....What ever you do be careful to protect your investment