It’s funny. We want the history of the car but honestly at this point in time…
Does it matter. Unless you take the engine apart and verify internals you have to assume the engine is stock.
The car is over 50 years old and you are not the original owner so assume it is completely modified until you verify everything vs going off the memory of people who wrote that car off years ago.
I wish you “good luck.” In your quest. But sadly, without knowing the car it’s entire life, you need to spend a lot of energy and possibly getting no where.
Syleng1