By the position of the water pump this looks likes a 55 or later 235. A 54 water pump will be positioned to nearly to the bottom of the water (thermostat) outlet. The water pump in the photo you included appears to be lower. The 55 or later 235 actually has a better water pump design. Patrick's Truck Parts in AZ. (http://www.patricksantiquecars.com/ call or request a catolog) has a reproduction radiator designed to accommodate the later 235 in the 54 and older trucks.

Hope this helps
Walt Williams
La Verkin, UT