By no means can you compare a dmax to those old dinosaurs. Completely different fuel injection system as well as much better computer controls and engine engineering in a dmax.
7.3s live off glow plugs when they cold start. If they don't have good plugs, they don't start for crap even in warm weather. A duramax may cough and sputter on a cold cold morning with a few glow plugs out but it will fire up
Duramax doesn't need glow plugs or a grid heater until 30* I've been 15* and it takes a bit of cranking and it isn't happy but it always starts.