UPDATE (JULY 27, 2012): This method is outdated, since OS X Mountain Lion and Mac OS X Lion 10.7.5 have added native support for the NVIDIA 600 series.
The method described in this guide involves installing graphics drivers taken from the recent software update for Apple's new Macbook Pro. In theory, this method should work with all graphics cards in the 600 series. However, it has only been tested for the GTX 670. It's recommended that you make a backup of your Hackintosh's hard drive before attempting this method, since you'll be changing a lot of important system files.
1. Update to Mac OS X 10.7.4
The new graphics drivers for the GTX 600 series only work with Mac OS X Lion version 10.7.4, so update your Hackintosh to Mac OS X 10.7.4.
Mac OS X Lion installation guide for more information.
2. Create a Unibeast USB drive for Mac OS X 10.7.4
In addition to updating your actual Hackintosh, you have to create a Unibeast USB drive for Mac OS X 10.7.4 as well. You will need this Unibeast USB drive to reinstall some system files in Mac OS X Lion later on.
To work, Unibeast requires the Mac OS X Lion installer app from the Mac App Store. Unless you set up your Hackintosh very recently, your copy of the Mac OS X Lion installer will probably be older than version 10.7.4, so you'll have to update it. You can usually do this by opening the Mac App Store and going to the "Updates" section. Once there, you'll see the option to update "OS X Lion".
Once you have the newest version of the Lion installer app, run Unibeast. For more details, check out Step 1 and Step 2 of our Mac OS X Lion installation guide.
3. Install netkas' drivers
Download the drivers that netkas has uploaded (it's a 130 MB download). These drivers will come in a .pkg installer file.
DOWNLOAD: ati and nvidia drivers from MBP2012 for 10.7.4.pkg
After completing the download, run the .pkg installer to install the graphics drivers. Then reboot your Hackintosh.
4. Reinstall Lion from your Unibeast USB drive
Installing netkas' drivers will break your Hackintosh, and prevent you from getting past the login screen of Mac OS X. Now you'll need to use your Unibeast USB drive to fix this. Plug your Unibeast USB drive into your computer, and let the Unibeast boot screen come up.
Install Mac OS X Lion on top of your current hard drive. This will fix all of the files that the new graphics drivers broke. However, your Hackintosh will still be unable to boot by itself, since reinstalling Mac OS X Lion messes up your Hackintosh-specific kexts and drivers.
Restart your Hackintosh. Keep your Unibeast USB drive plugged into your Hackintosh, select your hard drive from the Unibeast boot screen, and boot into Mac OS X.
5. Install netkas' drivers again
Once you have booted into Mac OS X, run the .pkg installer from netkas (again), to install the graphics drivers one more time.
Reinstalling Mac OS X Lion will have removed all of your old Hackintosh-specific kexts and system files, so you'll have to reinstall all of those things with Multibeast.
tonymacx86.com, if you haven't already (you have to register on tonymacx86 to view the download section). Open Multibeast, and select the appropriate options. For more details, check out the Multibeast step (Step 7) in our Mac OS X Lion installation guide.
Once you've reinstalled all of the appropriate files for your Hackintosh, go on to the next step.
7. Turn off Graphics Enabler
The one catch to enabling the GTX 670 on Mac OS X Lion is that Graphics Enabler doesn't work. Graphics Enabler is a feature in Mac OS X that allows your Hackintosh to run games and other graphics-intensive programs. However, the GTX 600 series doesn't work with Graphics Enabler (yet), so you'll have to turn it off.
This is very easy with Multibeast. Open Multibeast, and select "64-bit GraphicsEnabler=No".
Once you've turned off Graphics Enabler, reboot.
8. You're done! (Ending Notes)
Once you've rebooted, you should have full screen resolution and graphics acceleration on your Hackintosh with the GTX 670. Congratulations.
However, remember that Graphics Enabler is turned off. This means that you will not be able to play most video games. In addition, you won't be able to run DVD Player, Geekbench, or several other apps that require Graphics Enabler.
SOURCE: How to get the gtx670 working in Lion