Since the headset is already wrong, my choice would be to get a modern Stronglight A9 headset, strip it of its anodizing with oven cleaner, polish it up until it looks like chrome, and then install. I am thinking that the stack height will be less than Edco, but I really don't know for certain.
Another choice is to find a cheapo french stem you don't care about and drill it like a spearpoint for a centerpull until you find a better solution. I have a raleigh/GB stem which is drilled just large enough for a cable housing ferrule. (counter sunk - ferrule goes only about 4mm into the stem, rest of the hole is only about 2-2.5mm wide.)
The mafac hanger is super-slim, like a washer. You could also take an A9 and grind away a little bit of the locknut, and a little bit of the top race, to make space for the super-slim centerpull washer, which is only about 1mm thick. I have an unused one if you are looking for one of these.
Best of luck,
- Don Gillies
San Diego, CA