They aren't compatible.

2005-2008 5.7 car
2006-2010 6.1 car

Those both interchange.

Anything 2009 and up 5.7 and 2011 and up 6.4 use the same cover.

I bought my eagle valve covers from http://car-part.com/ from a salvage yard around Michigan for about $100 shipped, and that was a good deal.