Here's the output of the installer.
nvidia-installer log file '/var/log/nvidia-installer.log'
creation time: Thu Jan 23 19:25:25 2014
installer version: 331.38
nvidia-installer command line:
Using: nvidia-installer ncurses user interface
WARNING: Skipping the runlevel check (the utility `runlevel` failed to run).
-> License accepted.
-> Installing NVIDIA driver version 331.38.
-> Performing CC sanity check with CC="cc".
ERROR: The kernel header file '/usr/src/linux-3.12.8-1-ARCH/include/linux/kernel.h' does not exist. The most likely reason for this is that the kernel source path '/usr/src/linux-3.12.8-1-ARCH' is incorrect. Please make sure you have installed the kernel source files for your kernel and that they are properly configured; on Red Hat Linux systems, for example, be sure you have the 'kernel-source' or 'kernel-devel' RPM installed. If you know the correct kernel source files are installed, you may specify the kernel source path with the '--kernel-source-path' command line option.
ERROR: Installation has failed. Please see the file '/var/log/nvidia-installer.log' for details. You may find suggestions on fixing installation problems in the README available on the Linux driver download page at www.nvidia.com