Here are locations of various head and block casting codes. The date casting codes will tell you when the head and block were cast. These codes plus the head and block casting codes will tell you what engine you have (and, when the head and block were cast).
216s and older 235 (1941-1949 235) engines have very similar characteristics. Can post photos? If yes, take close-up photos of where the water pump attaches to the block. If it is a 1954 and later 235/261, and the water pump is the original style, the water pump body will be completely below the head.
Also, all 216 engines and all pre-53 235 engine had an oil-distributor
on the manifold side of the block. If you provide enough information, people will be able to tell you what engine you have.
Finally, if you simply want to quickly determine if you have a pre-1953 engine or a 1954 and later engine, take off the valve cover and count the number of head bolts (15 bolts on all 216s and on earlier 235s, and 18 bolts on later 235s and all 261s).
