I imagine a lot of these big brutes were used for towing. I remember back in 1966 there was a 1966 Impala 4 door sedan on our local Army Base. It had a 427 and a good sized trailer was in the driveway. However, a 427 Caprice four door hardtop could very well have been ordered as a luxurious highway cruiser.
Man, that Caprice would cruise on the thruway and be so comfortable