Al capone's Cadillac was Used by President Roosevelt after the attack on pearl harbor. The 1928 cadillac had bullet proof windows, armored plating and was painted green with black fenders to look like a police car.
1938 Cadillac LaSalle 5059 Convertible Sedan - the Mob Gang needs status symbol cars to show their connection. A big powerful roadster is such a car. It serves notice, that these men mean business. Today, it would be Cadillac XTS.