Somewhat related - I recently bought rear pads for my 2011 G37. Even went as far as getting OEM ones from a friend that works at Nissan.
Finally had the time to install them, and wouldnt you know...they dont fit. They had 2 locating "nubs" on them that the stock pads didnt. Those nubs prevented the installation of the existing shims and heat shields.
I went and got a set of aftermarket pads. And wouldn't you know? Same damn nubs.
Moral of the story: somewhere along the line stuff can change. In my case Nissan must have changed the shims and heat shields, but the new ones are a special order part in a $50.00 hardware kit. My solution? Grind down the nubs, spot paint over the exposed metal, install pads.