Date code on stock exhaust manifold
It is an age old story, people often want absolute facts when there are none to offer.
One of my 1970 cars was 'scheduled' 417.
The original engine in it was completed as an assembly on 422.
It had a door sticker showing it was completed in April, so I knew it was finished before May.
The oldest date codes I found on it were three pieces of side glass - June of 1969.
We can record facts for any original car as found, but guesses lead to lies & misinformation as a result.