My '94 SC2 went about 7 years parked outside during Wisconsin winters with years where the temp stayed around zero for weeks at a time, with occasional dips as far as -40 (and that's without the windchill figured in). During that time, gas-line antifreeze additive, synthetic oil, fresh coolant anti-freeze, and the most powerful CCA battery that fits in the car did the job. Started up every morning with no problems, and I never had the need for a block/battery heater.
Make sure you also have a relatively new thermostat so the inside of the vehicle heats up as quickly as possible once the car gets running. And you'll probably want to replace your battery every 2 to 3 years as preventative maintenance. I've had two batteries out of 3 die in the middle of winter right at the 3 year mark, and I cannot stress how much it sucks to have to replace a battery with the car outdoors when it is that cold.
Lane [ lane (at) evilplastic.com ] (Has changed the oil outdoors at zero degrees. Bring it on.)