I looked at a bunch of pictures. Here's my observation.
First, most pictures were taken during time at the docks, in fact almost all. Unloading, if on a boom, you assume whatever protection was on there is removed.
For trucks with steel cabs roofs, the glass sometimes looks to be covered individually with panels held on by straps.
That would seem to make sense, if Dodge makes 250,000 half ton trucks, some with cabs, not hard to make shipping covers too.
Trucks with open cabs, some have a wood box over the windscreen.