RE: Picked up some old stuff. Questions.....
The OS engine is actually better (personal thought) than offered today. I've flown many OS & Enya FS engines and can tell you from experience that you will come to love the push rods being behind the cylinder when you have a mishap. The push rods mounted forward of the cylinder can (and will) take a beating. Too bad you ran the engine, it's value is now reduced to half of what it could have been. Many folks would like to find a "never mounted" and/or "never run" older OS90 FS. As far as the plug goes, if you're uncomfortable with it being so close to the prop try a remote glow setup.
Enjoy your new stuff!
Randy