Continuing Carroll Shelby's legacy, Shelby American is known for making stock Ford Mustangs even faster and more extreme. At the SEMA show last month, the Las Vegas-based tuner revealed its first EV based on the Ford Mustang Mach-E. Next month, Shelby American will reveal its latest modified Mustang, and this promises to be something special.

On social media, Shelby American has released a teaser image showing a new model hiding under a sheet with a pronounced rear spoiler, announcing that "something special will be revealed" on December 15, but that's all we have to go on. So let the speculation begin.

December 15 happens to be a significant date for Shelby American. On this day in 2009, Shelby Automobiles became Shelby American again. Shelby could have another corporate announcement to coincide with the anniversary, but the teaser suggests the tuner will reveal a new modified Mustang. The 2009 announcement coincided with the 45th anniversary of the GT350, so it's possible that Shelby American could revive the GT350 after it was discontinued by Ford and replaced with the Mach 1.

Alternatively, this new monster Mustang could be based on the GT500. After the last-generation GT500 was revived in 2007, Shelby brought back the GT500KR, which starred in the rebooted Knight Rider series. We know a new Knight Rider movie is in the works, so Shelby American could reveal a new GT500KR based on the current-generation GT500 for the new movie.

The previous GT500KR packed a 5.4-liter supercharged V8 producing 540 horsepower, which was 40 percent more than the standard GT500 at the time. Alternatively, Shelby could unveil a new Super Snake based on the GT500 or bring back the insane Shelby 1000. Available for the 2011-2014 Mustang GT500, the Shelby 1000 was the fastest Mustang Shelby American had ever built. Two variants were offered including a road-going version with 920 hp and a track-only version with 1,100 horsepower.

Whatever the case, we'll find out what Shelby American has been cooking up on December 15.