Shims were used on all 216s, and 1954 and later engines, if needed (check the Shop Manuals). I have rebuilt 1954&1960 235&261 engines that needed no shims (using reground crankshafts for over-sized bearings).
That 1957 date code on a 1954/55-1st-style truck block would have (obviously?) been on a replacement block for the higher-water-pump, higher-pressure engine, as suggested above (a 1954/55-1st engine). This is the first time that I recall someone posting this information but it is certainly a logical possibility.
