Burned out .09 and .15 glow heads for Nelson conversion

This more than likely won't work. By the time the taper is machined needed for the bottom seat of the Nelson plug, there may not be enough material left to have enough threads left. As Andras mentions, the Kamtechnik heads are currently available. Kamtechnik heads for the .09- .15 are setup for turbo plugs. The Nelson plugs are no longer produced and are currently made overseas. I'm told the quality of the Italian plugs are pretty satisfactory. The price that Henry was selling them at though has doubled for the new replacements.