Derived from the American, the Tarpon was the car that AMC could have, should have, but didn't make in response to the Mustang. Instead AMC built the Marlin, which, on the larger Classic chassis, was too big to be a pony car, too slow to be a muscle car, and cursed with ungainly proportions due to the Classic's stubby hood. The Tarpon wasn't perfect, either, but its awkward side window treatment (which prefigured the Marlin's) could have been fixed easily, along with some tweaks to the stock American front end, to create a convincing sporty car. First shown in January 1964, the Tarpon was well-received, but the project was moved to the Classic platform because AMC lacked a small V-8 to fit in the smaller car. By 1966 AMC had fit the new 290 into a slightly elongated American, but by then the Marlin was in the second year of its unsuccessful run.

source: amxfiles.com