WOW! A 1990?
I never plowed with anything that new before! My Newest Dodge plow truck was an 80 chassis under my 50 cab, and before that was the old 77. I have never had a problem with my old Dodges starting when it got cold. Many years ago we had a string of about a week of consistent -25 to -30 temps. The only 2 cars on our whole block that would start were my 2 Mopars.
If you can get it in where it can dry off without freezing, get it a bath. The seals on the doors like to freeze them closed if they freeze before they get dry.
The salt kills them, but the new stuff they cover the roads with around here is worse then the salt. Gene