Sorry, didn't see the schematic. Can the ceiling be raised? and is there an a/c unit?
There isn't an AC unit but one could easily be added as there is 1 or 2 roof vents, so it would just need to be mounted. The ceiling is fiberglass that allows light thru, it is unchanged in the cab but in the rest of the truck a drop ceiling was added, most likely to hide wiring and fluorescent light fixtures and to make it easier to add the stainless/plastic roof sections. So, yes, I suppose the drop ceiling could be raised or removed.