I don't think there is room for the kick plate to go outwardly. Take a look at pictures. Maybe could get some dimentions on an other 55 1st truck. From the edge of the motor hole or one of the bracket holes to the edge of the fresh air opening?
You can see in one of the photos of the firewall that the motor is lined up and brackets are in holes. Another shows that the heater is "too big" to fit.
http://www.flickr.com/photos/101977815@N04/
