LOL Grins you should come to ND... Cold is the national past time in the winter.. -65 degrees F with the Wind Chill on the really bad days. only -20 to -30 without the wind chill..5 watts per gallon, 5x75=375
I'd go with (2) 200 watt heaters. Your area is beautiful this time of year by the way. Too cold for me in the winter though, been there done that.