You oughtta take a look at the electrodes. They're called "massive electrodes" in many cases and in no way resemble what we normally use. To qualify for use in full scale the plug has to be FAA/PMA/STC.

You can't believe how much that adds ot the cost of parts. In my old C-150 a legal replacement generator cost about $450.00 at the time. You could take one out of a Chevy and run for years for $55.00. It was essentially the same generator. Don't ask how I know...