just found two more items:
http://www.autogeek.net/tire-supports.html
and from a Corvette forum.... I thought this was a very good option:
...I would jack the car up put wood blocks under the suspension arms just thick enough to keep the tires from touching the ground. This will keep the suspension loaded as it normally is with the tires off the ground. This set up will allow you to start the car and run thru the gears provided your storage spot has sufficient ventilation.
Mark