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While the majority of the full scale piston stuff does use the massive electrode style plugs, there are fine wire versions available which usually have nearly twice the service life but also cost about twice as much. Also there are two electrodes on nearly every full scale plug I've ever seen with the exception of some AC plugs that actually had three electrodes, but the biggest requirement is indeed that they be FAA/PMA approved. While I've never played with the stuff that does not use an engine actually designed for A/C use, an STC would cover that as well.

As for running a regular automotive type AC Delco generators/regulators/parts etc. on full scale A/C, I have no recollection of having done that...