You can install your GCC manually
either through
sudo port install gcc46
or your download the source code from one of the mirrors from here for example here
tar xzvf gcc-4.6.0.tar.gz cd gcc-4.6.0 ./configure make
well if you have multiple version, then through you can choose one
port select --list gcc
remember port
on mac is called macport https://www.macports.org/install.php
and add add the bin into your path export PATH=$PATH:/opt/local/bin