I tried fitting a different coil to an Echo blower for the Jims man who does my lawns, because after chasing around the only coil I could get for that Echo was going to cost $90 plus postage. I spent quite a long time cutting housing bits to fit a coil that was sort of close but in the end timing must have been slightly off because I was unable to get it to fire, but at least it had spark. I told him to ask at their Jims meeting if anybody had that model Echo that had seized or had just worn out, but spark was ok.
So sparker I have tried but not had success