I was able to create a clean save file, nothing unlocked, that has been linked to the mario kart bonus disc to unlock the available extras.
I didn't see any save files online that had the gcn link extras unlocked without having numerous other extras unlocked already, such as supports and sound tests.
I'm not sure if anyone will find this useful, but I felt that after taking the time to create the save, I should share it with the community.
Frosty
Fire Emblem (USA, Australia).sav