Judging from this past weeks BJ auction, it could be worth anything from 70k - 200k!! What is the end game? I think if I were building that car to sell as much as I like originality I would put a modern ls or whatever they are called motor in it. Upgrade suspension, the interior can be pretty much stock, maybe re work the console to add some sort of touch screen something crap. That is the kind of car getting big money right now.
If the car is built to original specs, without correct drivetrain (I doubt it will hurt the value significantly, a corvette yes, trans am, not so much) I would think it would sell at auction easily for 60k+