IMO, the shipping crate may be factory original, but the engine as described sounds like it possibly was the engine taken out of the car when the crate engine was dropped in and the crate was used for storage. To my knowledge, there was never a factory GM crate engine that came with Edelbrock valve covers or 2 Holley 4bbl carbs. Even the twin Holley cross ram intakes used on the early Z-28 302 engines were dealer installed options, not complete engines. I agree with Don, pictures would tell the rest of the story.

Mike