A few decades ago, I had a friend named Rich, who owned one of these. His family were serious car collectors, with a very eclectic stable of vehicles.
Rich’s Biarritz was named Bertha, and it still had its functioning Air Suspension, which was problematic as they aged, and many owners had them converted to normal shock absorbers. The car actually lowered itself when parked.
Also: ALL Cadillacs that/these years had 365 cubic-inch engines, making 300 horsepower. I had a ’57 DeVille with one. The Eldo’s did have more horsepower, with their larger carburetors.
It’s worth mentioning that 1958 was the year that quad headlights were made legal. The 1957 Eldorado Brougham somehow got to have them a year earlier.