first off by looking at your picture l would make sure your flywheel is rust free and also clean the coil (u can do this with emery cloth/fine sand paper or an sos pad), before u say the coil is no good. but in my experince coils rarely go bad and by this picture l'm looking at theres a good chance its to rusty!!, l assume u replaced the spark plug?, the only other thing it could be is the ground wire has a short to ground some where (bare wire touching the block).lets say the coil is bad than yes u will need a air gap of 0.10. the spark plug wire is not replacable on its own.
The coil isn't bad, AFAIK. The wire end, connection to the spark plug (new plug) has corroded and broken off, so I need to replace the wire. As you and whitetail say, it looks like there's no way to replace the wire (I guess it's different than on cars...), so it sounds like this is the part to replace...
Thanks for the info -- I'll post back with my results once I get the part.