If you are on the UP of Michigan it is a state law that you must have a tractor cab!!

That is a great looking machine you have!
A lot of good suggestions already posted.
On my old Ford, I would grab the radiator hose, that would tell me if I needed more time to heat or if it was ready. Sometimes it would tell me the block heater wasn't plugged in!
At -15 degrees I am also thinking you may have been lacking on Cold Cranking Amps. In those temps batteries lose some of their capacity.
In cunjunction with my block heater, when it was below 25F , I would also plug in my 2amp trickle charger. You can't leave a trickle charger on for long periods, but for a couple hours, in conjunction with the block heater, should give you a few more Cranking amps to turn over the motor.
I wired a small 2-conducter plug wire to my battery terminals, and brought them up near the steering column so I could plug in the trickle charger without raising the hood.
If it was sitting outdoors in cold and wind, I would place an old moving blanket over the hood, which would help keep in some of the heat created.
If it's windy, a piece of chain draped over the blanket a few times would keep the blanket from blowing off.
Also, if I knew I was getting up at O-dark-30 to plow snow, I would use a timer, set it up the evening before, and have it come on about 3 a.m. , that way by the time I got out there, the block heater and trickle charger had been on for a few hours and it would crank much easier.