I have to agree with Henry. Old hoses, belts, plastics, etc are a bigger issue on an old vehicle at the mid -20°F temps.
-34°F is the start of ice crystal formation on a 50:50 mix. You will not freeze up and damage an engine at -34°F using that mixture.
You're only getting -25°F at the worst of this. At -25°F Wind Chill numbers near the -40° range is a "Feels like" number. It just means at higher wind speeds vehicles, pets, and humans don't take as long to get down to actual temp of -25°F so don't expose your skin to the blowing wind.
I grew up in Central NY farming country between Binghamton and Syracuse and then Upstate in Hoosick Falls NY just outside Bennington Vt and North Adams Ma.
I've only seen -35°F in Sherburne NY once... Over Christmas 1981 or 1980. It set a bunch of records. Alba-Schenecta-Troy, Lake George, and Plattsburgh generally run higher temps in the winter than the higher elevations around Cooperstown, New Berlin, Sherburne, Hamilton, and Norwich. We always ran 50:50 in everything.
Most of these trucks are not daily drivers anymore. Since they primarily operate in summer weather heat is more worrisome. 50:50 transfers heat better than 60:40 or 70:30.