NVidia driver 349.90 is available from Windows Updates for those people on Windows 10.
When the driver comes in, there are actually 4 different files that show up in C:\Windows\System32\DriverStore\FileRepository.
The main one for 64-bit desktop cards is here: http://www.mediafire.com/download/1jk45es6dequgc8/nv_dispiwu.inf_amd64_01b8665b88b69f49.zip
For some desktop cards a modified inf file may be necessary.
DX12 Runtime version is 12.0 and Direct3D API version is 12.
Driver 349.90 is MS349_27-29, DriverVer = 03/11/2015, 9.18.13.4990
Driver 347.88 is r346_00-386, DriverVer = 03/13/2015, 9.18.13.4788
Driver 347.71 is r347_52-2, DriverVer = 02/26/2015, 9.18.13.4771
Driver 347.62 is r346_00-339, DriverVer = 02/17/2015, 9.18.13.4762
Driver 347.52 is r346_00-321, DriverVer = 02/05/2015, 9.18.13.4752
Driver 349.65 is MS349_27-21, DriverVer = 02/05/2015, 9.18.13.4965