I don't think this will work.
If you are trying to deal with an 8 bit binary file as text, the text editor will do all kinds of weird things while both opening and saving the file.
Text editors usually only work with 7 bit ASCII and they always respond to the control characters as control characters.
You might get away with doing a global substitution in a genuine HEX editor.
If you can prove that all you need to do is exchange a few bytes in the headers, then I could cook up a very reliable conversion utility in LaserBoy.
That would be trivial, I think.
If it is in fact the case that they just swapped out a few ASCII characters in the headers of ILDA format 0, the reason they did it was to separate their format from the generic standard and so that they do not need to comply with any of the "correct" ILDA format standards.
James.