The snouts are interchangeable but due to where the cobalt's supercharger is located it is longer than the benz one and wouldn't line up with the belt. Also a general rule of thumb is every 1/10" smaller is about 1psi extra. Also it is a press fit type, Eaton confirmed it was, the pulley just has an integrated clutch. There is a tool to remove and install the pulleys.

http://www.pulleyboys.com/M62.pdf

I'm working on finding out the pulley offset and inside diameter to see if they match up with Nissan pulleys. If they do then we are in business. If not then at least we have the specs to make our own.