The easiest way to determine what came on the engine from the engine plant and what was installed at the car assembly plant is to look in the assembly manual; anything that has a part number callout was installed at the car assembly plant, and anything that doesn't came as part of the engine assembly as shipped from the engine plant.
Chevrolet engines were pretty bare-naked leaving the engine plant, as posted above; automatic engines just had a flexplate, and manuals had the flywheel, clutch, bellhousing, and clutch fork. Other than the distributor, that was about it, except for the orange-painted parts.
Here's a photo from the shipping dock at Flint Engine, taken in 1955; engine state of dress at that point didn't change until the early 80's.
