actually the cap you seek has been used in many applications within the GM house (Chevy, Buick, Caddy....etc) until I can lay my hands on a C7 non-z51 to verify the fit, but it can be found for less then $10. even at GMPARTSDIRECT.com, Amazon, and Ebay. but just by looking at the images. this will work.
GM P/N 12577268 (the current cap with dexos on it is 12643759)
