Think outside the box and use your imagination...
On the computer:
Choose a pic of flat faced bus. Overlay a pic of a trolley (or rail car) whose style you like. Stretch to get it lined up. Print the trolley out on regular paper and the schoolbus on a sheet of translucent tracing paper. Lay the schoolbus over the trolly and use a pencil to sketch in the trolley attributes you want.You will need to shift the paper around. Don't worry about scale at this point. Use a white craft eraser on the paper (I buy mine from DollarTree). You are making a "faux" trolly.. you will have "faux windows, you really don't want clear glass everywhere... use a "faux" frost (paint) with "mirror" solar film on plastic. Attach to the outside of the bus and trim out with "faux" wood (PVC.. doesn't rot, paint as desired). Use overlay trim to turn rectangular windows into arched windows. Clearstory in roof... Good place to run a roof top AC unit and ductwork (don't make too high... stay under 12'6" overall). Inside: recess lights and build down a 1" frame to accept plastic ceiling panels (use velco to keep from falling out). Paint PVC pipe brass for all the brass railing. Check out places like Renovators Supply or Van Dyke Restorers, mags/books on Victorian stuff. And when you look at pics in the mags/books onVictorian stuff, bear in mind that, in many cases, ORIGINALLY the marble, fancy woods, leathers, plaster and metals were "faux" or very thin veneers.
With a little "tweaking" , we could create a flat fronted bus that would look very close to the top pic. I would not have operational windows for most of the unit as they let in a lot of cold air in the winter and windows "get in the way" of cabinets and closets. The clearstory could be "opened" in a spot or two inside to add a little height between roof ribs and the side windows could be real in those spots and could let light in. Or they could all be simply white panels covering a few light bulbs that could be lit up at night.
Use your imagination. This method will help you visualize how to turn any bus into almost anything. It's all an illusion.
Flame on....