I don't know if there's any smarter way of doing this, but I took a look at some of the fixed 93C56 files posted here in a hex editor. A lot of the data is identical or empty in all of them, and I could use that insight to fix one myself. I put together this gif to make it easier to see which data is identical in all of the dumps. If your dump has different data in those areas, there's a good chance that you can just change it to be identical with the other dumps and it'll work fine. I don't know what any of the variable data is, but I have a sneaking suspicion that corruption there isn't as critical.
It should also be noted that the two 220 µF/10 V capacitors in this ECU go bad and should be replaced when doing this repair. I suspect that they might be a part of what causes this problem.
I used an 809H universal programmer to read and write the chip, though I had to desolder it for that to work.
I hope this can be of help to someone!
EDIT: The forum engine automatically turns gifs into jpgs (why?!), so I had to put it in a .zip.
Attachment 967904
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