Look what the mail man dropped at the door today

Are you sure from a Buick straight 8? The Mopar 340 TA engine of the early 70's had adjustable rockers, similar to a 273 (forged), but offset to allow bigger intake ports. Don't know if the rocker shaft diameter was the same as a slant. The little hole in the top might be a give-away. Does that squirt oil or such?