Based on a 54(? [According to the CL ad]) pax International conventional bus . Been looking around for cheap used buses to convert, and may have a lead on one, so the floor plan is mutable. I'm planning on having a wet bath for the head; the transparencies (clear blue squares) are sky lights, probably replacing or modifying the escape hatches. Bunks are located over the rear wheel wells. Deleted windows will be either painted over and insulated from the inside or skinned over with sheet steel.
Done in MS Visio, with the driver's seat, console, stairs and floor sections from ProFantasy's Campaign Cartographer with Cosmographer add on.