I just set this up and there was one gotcha, the syntax is slightly different at least on my version (OpenSSH_6.6p1 Ubuntu-2ubuntu1).

The LocalForward and RemoteForward takes two arguments instead of one, so I had to use:

    LocalForward localhost:8000 localhost:80

There were a lot of examples online of the syntax being just like the command line, so mine's either very outdated or it was recently changed.