Slapping the V10 from a BMW M5 into its little brother, the M3, isn't a new idea (Hartge's been there and done that). What's new is putting that V10 into the 2008 M3, which sports a V10-derived 4.0-liter V8 producing 420 horsepower. As covered in a thread on M3Post, German aftermarket supplier Bremgo made that swap, resulting in 507 horsepower, and an engine bay that looks like something Mr. Gestalt threw together in his spare time. The finished product was recently spotted at the Nürburgring, where it was likely undergoing some manner of shakedown, or just a bit of fun. Maybe it'll be in Frankfurt; who knows? [via M3Post]