Joe...I would not sell this engine...anyplace except eBay! You will get the best price for it there, by quite a lot. Just speculating, I'd expect over $200, with $300 being reasonable, especially if you have box, literature, and any wrenches, etc. That Fox glowplug has to go, however. If you can find a Taylor or Enya plug, that should help bring more money...the stranger the better. Try Randy Aero for Enya glowplugs.
It is a little beauty, that's for sure.
Don't mount it, or run it, if you haven't yet.
Good luck flying any combat event against "The Alien"!
Steve