just renaming the game or save to either should work. make sure both the game and save file have the exact same name so it can work
well. i ususally name my game with their respective name. so in pokemon white (J), i had it named Pokemon White.nds and its sav file was Pokemon White.sav . once i downloaded the (E) version i copied the name of the sav file i had to the (E) version rom, renaming it to Pokemon White.nds