A list of the fastest-rising muscle cars in terms of auction values includes many cars that are rare and valuable today because, when they were new, nobody wanted them. The list was compiled by the collector car editors at Kelley Blue Book.
1969 Dodge Charger
Of the top 10, four are convertibles with big race-tuned engines. (That number doesn't include one stray two-seat convertible that, technically speaking, you might not want to count as a muscle car.) That combination was unpopular with buyers at the time for a couple of reasons.
First, it was incredibly expensive. Second, it made little sense: What was the point of buying a high-output engine only to add weight with a convertible top?
Full list here