Q: In this task, you're given a passage, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both passage and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the passage or linked information.
Passage: The Mustang's success left General Motors unprepared. Chrysler introduced the Plymouth Barracuda a few weeks before the Mustang, and although it was later redesigned as a distinct "pony car", it was initially a modified Plymouth Valiant. However, the "fish car" did not enjoy as strong a market demand as Ford's "pony". General Motors executives thought the rear-engined Chevrolet Corvair Monza would compete against the Mustang, but it also sold poorly by comparison. The Monza performed well, but lacked a V8 engine and its reputation was tarnished by Ralph Nader in his book Unsafe At Any Speed. It took GM until the 1967 model year to counter with the Chevrolet Camaro and Pontiac Firebird. Lincoln-Mercury joined the competition in 1966 with the Mercury Cougar, an "upmarket Mustang" and subsequent Motor Trend Car of the Year. In 1967, American Motors (AMC) introduced the Javelin, an image changing "standout" four-place pony car. In 1969, the Dodge Challenger, a version of the Plymouth Barracuda platform, was last to join the pony car race. This genre of small, sporty automobiles is often referred to as the "pony car" because of the Ford Mustang that established this market segment.
Link Information: none Answer: none
A:
Which of the two car models that GM used to counter the Plymouth Barracuda in 1967 sold the most units?