I'm going to agree with you guys that are saying buy a winter beater.
Last year I bought a (slightly rusty) festiva for $250, drove it through the winter, then sold it for $350.
2 of the 4 winter beaters I bought are out of commission due to people crashing into me during the winter. Which is worse: losing 2x $500 economy cars (great gas mileage before they were wrecked), or losing a classic Z car at $1000 - $10,000?
My current winter car is a nice little AWD Impreza that I got off ebay for $850(us). A couple hundred into winter tires and I not only spare the Z, but actually ENJOY driving in the snow and ice.
It's not a bad idea to put a little effort into making your Z more rust resistant, especially if you live in a rainy area, but DO NOT drive it in the winter. If you MUST drive it all year around, move to Texas.