Order of assembly? From a bare shell

Just a personal preference, like Kursplat said. Body color on underside(unless black) and welcome to tedious cleaning and constant touch ups.
What is wrong with using white underneath there on a white car?

I don't remember that all Mopars were black underneath.
I do know that Mopar people have a conniption fit if you paint under the hood black unless it's a black car.