As we predicted earlier this year, the third-generation Mercedes-Benz SLK in AMG trim will be receiving a new heart transplant in the form of a naturally aspirated version of the twin-turbocharged 5.5-liter sledgehammer V-8 making its way into most of the Affalterbach tuner’s lineup.

We can now reveal that this AMG version of the latest SLK will keep its “SLK55 AMG” title and will deliver a peak output of 422 horsepower at 6,800 rpm and 398 pound-feet of torque at 4,500 rpm. In case you’re wondering, that’s a full 62 horsepower more than the outgoing model’s 5.4-liter V-8.

So when might we see the new Mercedes-Benz SLK55 AMG? Its world debut is scheduled to take place at the 2011 Frankfurt Auto Show this September, which means we can expect the new car in showrooms by early next year--at the latest.

Without the turbos, the engine, now codenamed M152, weighs in at 412 pounds. Fuel saving features include advanced cylinder deactivation, which will allow it to run on just four cylinders during low load situations, as well as an autonomous stop-start system and direct injection technology.

An adjustable exhaust system will also feature, allowing the car to be relatively quiet at pedestrian speeds and a wailing banshee when the throttle is floored.

Look out for the debut of the Mercedes-Benz SLK55 AMG this September in Frankfurt, where a new diesel version of the SLK should also debut. While you wait for their respective reveals, click here to view our mega-gallery of the latest 2012 Mercedes-Benz SLK.