Tru64 5.1B GCC-4.4.7 
--------------------

Download the tarball from GCC-4.4.7 and extract in / 

# mkdir /data
# mv gcc447.tar /data 
# cd /data 
# tar -xvf gcc447.tar 
# rm -f gcc447.tar 

GCC will be extracted to /data/gcc447 
Next create symlink 

# cd /usr/local/lib 
# ln -s /usr/data/gcc447/lib/libgcc_s.so.1 /usr/local/lib/libgcc_s.so.1 

Add the /data/gcc447/bin path to your environment variables   

PATH=/sbin:/usr/sbin:/usr/bin:/usr/ccs/bin:/usr/bin/X11:/usr/local/bin:/usr/data/gcc447/bin
export PATH

Now you should be able to run gcc 

root@tru64 ~# gcc -v
Using built-in specs.
Target: alphaev67-dec-osf5.1b
Configured with: ./configure --prefix=/data/gcc447 --enable-threads=posix --disable-nls --enable-languages=c,c++ --without-gnu-ld --with-ld=/usr/ccs/bin/ld --without-gnu-as --with-as=/usr/bin/as --disable-libssp --with-libiconv-prefix=/usr/local --with-gmp=/usr/local --with-mpfr=/usr/local
Thread model: posix
gcc version 4.4.7 (GCC)