I've told this story before...
There's a local guy with a nice '70 Challenger he bought brand new. 340 car, super original and clean.
Somewhere along the line, the pie tin on the air cleaner got switched or the wrong one was installed. It says "383 Magnum" on it. This guy is 100% convinced that the car is a small block 383. He even says he has a letter from the factory about it...
He has a lot of very, very nice cars that you can't find too much fault with. All supposed to be "original" and not restored and I believe that... But they all are "one of one" according to him. Yea, they are low production cars, and again, very nice examples, but not "one of one". He has signs that go with the cars and I really think he's been telling these stories so long he believes them himself.