Please check for the partial vin on the 302, may help someone looking for their original block. It is hard to read in the rough casting but can be done.
I would also suggest going back with the blue vinyl top and interior. One thing I see is buyers looking for unique cars, and when done, it may create more of a buzz since it will present as a "1 of 1" type of exterior. Even though most cars are riding a high right now (including 1st gen Camaros), even with a future market correction I think if you and your gramps do the labor, and turn it out stock, finding some original dated parts along the way, you would not lose money if you wanted to sell. just my 2 cents