1969 silver 383 cuda a57 pic. Heavy!!!!
Lots to think about here and the direction you will take.
Unfortunately with only a vin as documentation you can only prove that it was a 383 car.......
While I have no doubts that it is an A57 car and was/is silver your value potential is limited because of the lack of documentation and drive-train.
I wouldn't worry about rarity of the color, special order or any of that silliness...... Because none of it matters at this point.
Build it how you want it and enjoy.
http://www.hamtramck-historical.com/dealerships/1969PlymouthDealershipDataBook-01.shtml