Pulling a trailer with one of these? You DA MAN!! ;)
Not sure why it takes so long to heat up. Looking into it a bit more the motor has two cooling circuits: one for the block and one for the head itself.
Heat to the passenger compartment is fed from coolant coming from the head so one would think it would heat up very quickly!
But this design was to ensure quick warm-up for the motor as a whole so who knows why it takes so long in really cold weather.