how bad is winter for an old car?

i know that sound extremely dumb to ask. but here's my scenario,

i have a good sized garage that can hold 1 car plus all my tools etc but with the car in it, i can't work on anything but that car. i have a few projects going on and i am thinking of getting one of those "car tent" things to keep the Dart in.

now new england winters can be brutal. deep cold, lots of snow, salt ice. obv the car would be covered and protected from elements but not as well as if it was in the garage.

the car is a driver - nothing super fancy. not to say i don't like the car - far from it. i dont want it to deteriorate. but as my neighbor said - it's already 42 years old, i am sure it has seen rain and snow. and judgng from the rust underneath, i'd say he is right.

anyway just curious as to what you all think.