It's nice to see what an extra-tall (H3) looks like on the inside. Lots more storage space in the forehead! @Lolaeliz beat me to it. Ditching the cab partition and adding swivel seat-bases would also bring the cab seats into play in the living space and eliminate the need for additional seating, freeing up valuable space for other stuff.
Here is a handy floorplan helper. Your L4 has the same floor footprint as the Promaster Long Body diagram. However, the L4 over here is properly called a Promaster 3500 EXT, but it only comes in H2 here.
Here is a handy floorplan helper. Your L4 has the same floor footprint as the Promaster Long Body diagram. However, the L4 over here is properly called a Promaster 3500 EXT, but it only comes in H2 here.