Downgrading packages in Ubuntu

So I needed to downgrade the version of my gzip package in Ubuntu 10.04 because it wouldn't work with my openembedded build (I was getting errors unpacking the expat tarball). What I ended up doing was adding the "hardy" packages to my list of sources through the software sources gui (deb http://security.ubuntu.com/ubuntu hardy-security main). Then I followed the instructions here to find the older version of gzip and downgrade it. Now my build works. Basically what I did was:

1. System->Administration->Software Sources
2. Go to Other software and click Add
3. Add the line above (deb http://security.ubuntu.com/ubuntu hardy-security main)
4. Click close and allow it to rebuild the database.
5. run apt-cache showpkg gzip
6. You'll see the versions. You want the 1.3.12-3.2ubuntu0.1 version
7. run sudo apt-get install gzip=1.3.12-3.2ubuntu0.1
8. Select yes when asked if you want to downgrade.