Hello.
I've managed to install windows 7 and 8,1 on my mac pro using
only a gtx 970 Non-EFI.
If you try to install windows with bootcamp assistant or via usb or by using your gt120 and then switching to your gtx 970 it will not work. (EFI Mode = black screen with blinking cursor with PC gtx970)
You
need to use a DVD and a secondary drive to install windows to.
Remove your OS X drive from your mac pro before installing.
Just reboot with a windows dvd in superdrive.
This will enable installation in "CSM mode".
Complete install.
Get the bootcamp drivers from
apple under windows.
Unzip it and remove all folders except Apple and Realtek ones under BootCamp5.1.5621\BootCamp\Drivers then launch BootCamp5.1.5621\BootCamp\setup.exe
Not cleaning up bootcamp drivers will break windows install / bootcamp drivers install.
Get drivers for gtx970 from nvidia website.
Never plug back your GT120 under windows or it will mess up GPU drivers and you will get a black screen.
Plug back OS X drive.
You can switch to windows from OS X with bootchamp. (
http://www.kainjow.com/)
When you reboot from windows you go back to OS X.
If you don't have a secondary drive this method is a no go.
Regards,