Remember that Benz Mule that was seen a few days ago? Turns out it may be for a different car altogether. From Autoblog:

Rumors of a gullwing revival have converged with recent spy shots showing a Mercedes supercar mule undergoing testing last week. According to Auto Motor und Sport, the new M.B. supercar, codenamed W198, will be built on a shortened SL platform and will house the 6.2-liter AMG V8 producing upwards of 600 HP.

The exterior design will take a few cues from Mercedes' iconic coupe of yore, but the retro theme has already been sent back once for being too evocative of the original.

The German buff book asserts that the W198 will make it to production sometime in 2010 with sales in the 3,000 to 5,000 range and priced between €140,000 and €200,000. Whether the Viper-based mule we've seen in spy shots will end up being the gullwing revival, the aluminum SLC, or whether both cars are one in the same, remains to be seen.
I'm having trouble saving the images from Auto Motor und Sport, so here is a link to the pics.