Wow, sub freezing all year? Where's that if I can ask...
I checked Stewart Components, and don't mind spending $30-$40 on a good thermostat, but I couldn't find one by them. Maybe I didn't look in the right place but it looked like they only have 9 on the entire site.
I would like to know where you got your 170 thermostat, what year engine you drive. I have searched a couple days for a 170 and can find tons of Chevy and Ford ones, but not Mopar for some reason. They make late model ones, but not the hot rod era.