[Stefano]

How do you know that any block, even it it does have a VIN is the original engine to a particular car?

Many times you can never know 100%.

Approx 612 L78 cars were produced so there were at least that many engines as well as some warranty replacement blocks produced. Not a very large number.

This particular engine has a chain of history as being in the general vicinity where this L78 Chevelle was sold new.

I'm confident that it was not the only one built on that day, but it does match the POP.

What are the odds that an L78 engine built on the same day would be found in the same area?

I stated that this is "believed" to be the original engine to this car, but can't say 100% for certain. Anyone interested would have to check out the story and make a determination for themselves.

Quite a bit of time and work (as well as capital) was invested to track the engine down and while it does not have a VIN, the pad date and suffix did turn out to match the car and POP.

It was at MCACN II and III.