The biggest enemy for long term storage of your FD is condensation forming INSIDE the engine.
I remember seeing piston aircraft engines (and we're talking engines worth $100K and up) being shipped with these funny little dessicant plugs installed instead of the spark plugs.
I've never seen them again until the other day in the Eastwood Company catalogue. www.eastwoodcompany.com
The cool thing is that they change from blue to pink when the dessicant becomes saturated so you know it's time for new ones.
At $7.99 each when you buy four I think it's the best thing you can do (including a fresh oil change) for long term storage. I would also put dessicant bags (available at camera stores) inside the tailpipe and intake as well and cover the openings with aluminum foil and rubber bands to seal it. Just remember to put a post-it-note on your steering wheel reminding you to remove them before starting the engine in the spring!!