there is gcc3 shipped with Mandy, you can install it off the CD's, then copy existing gcc executable to some off path location, and make a symlink from gcc3 to point to gcc, i.e
original gcc is located at /usr/bin/gcc the installed gcc3 is under /usr/local/gcc3. Your actions:
mv /usr/bin/gcc /misc/gcc.old
ln -sf /usr/local/bin/gcc3 /usr/bin/gcc
Side note: The actual paths to gcc and gcc3 binaries may vary, explore your system to find the right paths with which or locate commands.