1. Choose the package list of the Fatdog version you want to base on (e.g. 800).
2. Then, choose the builder whose "last modified" date matches or is close to the package list you have chosen in step 1.
3. Enjoy, and don't forget to share your builds with others.
Note: Because the packages are not historically preserved (we sometimes overrides packages containing known bugs with the corrected ones without changing the filenames), the build you have may not be bit-identical to the released Fatdog ISOs.