I then ran it on my 4.2 EEPROM dump (1024 bytes) and unfortunately the program only works on 512 sized EEPROMS. It reported "file must be 512 bytes."
You don't need any other tool except the ability to truncate the file to 512 bytes.
your clue is here in your very own post:
It's worth noting that my EEPROM on my 4.2L is a SP08C3 and is 1024 bytes. When I look at the BIN in a hex editor, 513-1024 is just all FF's. There's no data in that section of memory.