From at least 1948-1952 (I do not have a 1953 book),
216.5 engine was the only engine available on 1/2 ton through 1 ton trucks (3100-3900 series)
216.5 engine was standard on 1 1/2 ton trucks (4100-4500 series)
235.5 engine was optional on 1 1/2 ton trucks (4100-4500 series)
235.5 engine was standard on 2 ton trucks
