Help determining value

[amazon]

Need to set a price for my "de-licensed" 90 yr old FIL. He's the original owner of an '86 744 Turbo; Automatic; White/Grey fabric interior. It's been kept up well until last few years and now is burning oil big time so it's a candidate for a rebuild but will then be a super car. My wife won't let me take on another project although I'd love to. What might a car like this be worth to someone willing to take on a rebuild? TD
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