Debian Wheezy 7.5 in my BBB.
Linux beaglebone 3.8.13-bone50
With this command :
sudo apt-get install linux-headers-$(uname -r)
I got:
Unable to locate package linux-headers-3.8.13-bone50
Wheezy 7.5 is located here:
http://www.armhf.com/download/
The header file:
linux-headers-3.14.4.1-bone-armhf.com.tar.xz (June 3, 2014)
How to install it