As Breezy indicates my early 216 Canadian trucks had 1 1/4-inch thermostat housings and upper radiator hose connections and later 235 engines had 1 1/2-inch housings and upper radiator connections . The 1955 second series water pumps and lower radiator connections were 1 3/4-inch while the older models had 1 1/2-inch on the pump and radiator. Some vendors offer a lower hose with 1 1/2 inch on one end and 1/3/4 inch on the other to allow use of newer pumps with an older radiator.
