Yes, but then you need an original main.scm file.
1) Install clean gta3
2) Go to maps folder and backup main.scm file (rename it to old_main.scm or something)
3) Install Xbox Version mod
4) Go to maps folder again and delete new .scm file
5) Rename your backup .scm file back to 'main'
Then you can easily load your savegames
