Z87 G45 on newegg was discontinued because it ran out of stock all the time ( hot stuff plus 80$ discount for getting it with an i5, 100$ with an i7 ). There are no Z87 GD45, only Z87 GD65 which is 1 tier higher than the Z87 G45 in terms of features and OC potential.
The "Z87-GD45" on Amazon is simply the Z87 G45 named wrong. The image they used is wrong too. It belongs to the GD65, not the G45. MSI has never released a "Z87 GD45" model.