One of the last of these running in NYC was/is “disco cab” checker cab decked out with shag carpet and miniature disco balls. He’d pull up and shout “welcome to disco cab!”. Always playing funky 70s tunes. Miss that guy.
IIRC Marathon was the model name for the model as a non-fleet/taxi sedan. Same car. Different trim.
Casually people refer to the model as a marathon. And any cab built out of a civilian model is technically a Marathon rather than a number designated cab.
