Anyone know of a way to find the history of a 70?

[Hank70SS]

Derek pretty much covered it unless it's a Canadian built car. GM of Canada can provide documentation regarding the car and it's original options. Not a build sheet but good enough these days.

It should also have the frame supports, frame to rear upper control uppers as part of the F41 suspension. Since it has SS emblems on the doors it was most likely a 396, most 454's had Malibu emblems on the doors, don't ask me why. A 396 non-AC car would have a 3 core rad with the wider core support opening and 4 bolt top plate. That stuff may no longer be original. Also check the engine frame mounts, 307 had different frame/engine mounts.

Have the carpeting, door panels and gas tank been removed. These are typical places assembly line workers stuffed extra build sheets to get rid of them.