Back then, there were lots of 400+cid engine, with "lots" of cylinders making power. Back then, a "luxury" car owner had the luxury of getting the car into high gear and not having to downshift unless he had to stop and start again. Torque did that, which meant big engines and DEEP rear axle ratios (with the larger diameter tires of that time).
As all engines were mounted "solid" to the frame, the more cylinders in the engine, the smoother it ran and less vibration transferred into the passenger compartment. The old deal about being able to balance a dime (on its edge) on the intake manifold at idle, of a V-16 engine. OR was it a nickel? Either way, smooooth running was the implication.