speedometer in my 42-46 ford pickup

i asked some questions a few weeks ago concerning my serial nos on my ford pickkup the title says 42 but the frame and motor nos say 46 even though the truck frame is stamped 21c for the 42.it has the 116 inch wheel base with a 4 speed transmission.my question is it has a 60mph speedometer as if it were a big truck. does anyone know why this would have such all the other pickups i see have a 100mph speedometer thanks ps. this is appparently the one that came from the factory.