Semi-gloss black frame, with red oxide primer on the bottom of the sheet metal, body colored over spray along the edges. No over spray on the frame, it was attached later in the process!
Flat black for undercoating; along the transmission/driveshaft tunnel, as well as the the area under the rear axle. Amounts varied according to assembly plant and the guy spraying it! This coverage was the bare minimum, cars headed north would have more applied, usually at the dealership.
This should be accurate for 95% of GM intermediate cars of the 60s and 70s, or awfully darn close.