It is strange!
To confirm - you have a good spark at each plug and plugs are getting wet when you're cranking the engine over. That would suggest fuelling and ignition is OK.
It would suggest a timing issue? Can you get a rough idea of timing using the crank pulley timing marks? Static timing should give it enough to get it to start.
I wonder if it might be a problem with the dizzy shaft? Maybe the worm drive has sheared a tooth and she's skipped a few degrees.
I am not clear from the responses that there is a spark at the actual spark plug, only that there is current in the spark leads.
