Thank you for letting me know your appreciation for the game.
When moving from version 1.2 to 1.3 you should simply copy the TOPSCORES file from one disk to another. However, the same thing will not be done with the future version 1.4 which will have separate rankings based on the chosen game speed (PAL or NTSC), because the file will no longer be compatible. But if you are not interested in having separate rankings for the two different speeds, you can stick to version 1.3.