Are you sure your source is right? Because I have no doubt that this bus is a 1930/31 Ford Model AA, there are certain features that are unmistakable, two bar bumper with three oval clamps, radiator shell, bonnet, scuttle mounted petrol tank with centre filler cap, molding along bonnet and scuttle, wheels, headlights and front wings.
I found the puzzle picture in the famous coachwork site, it says 1926, but it doesn't
mention the maker of the chassis.