I just spent the last thirty minutes turning a burnt out Cox 049 glow head into a glow plug adapter. Put it on an engine (with a glow plug, of course), and it ran!
Well, at least it ran out the prime. I haven't tried it with actual fuel in the tank -- I'll want to do something more than just hold it in my hand for that. I'm 99.44% sure that it won't run as well as before, because it started out as a low-compression head, and the plug will lower the compression further (hence my sudden anal retentiveness about CCing heads).
Tomorrow I'll go see if it'll actually fly an airplane. Then maybe I'll think about how to turn some billet aluminum into a head.
Which means I'll have to make a special threading tool, so's I can thread right up to the edge of the fins. And a special fin-cutting tool, and a ...