How to add a header to FF3 1.0 without SnesTool

This is fairly easy if you have access to a hex editor. I don't know Windows 7 64-bit but if you are able to run in 32-bit Windows XP compatibility mode download Hex Workshop and simply open your rom and go to the Edit menu then Insert (or press CTRL+INS) and put in 200 hexadecimal bytes with 00 as the filler byte then save.

If this doesn't work then I cannot help you with a 64-bit Win7 operating system.