The number we really need to see is only partially visible. The stamped (not cast) number on the machined pad just behind the distributor will be more helpful in making an exact ID of the original application of the engine, as casting numbers have a tendency to apply across several production years and different original installations. An original equipment engine in a 53 3100 would have been a 216 with Babbit connecting rods, and the engine in your pics appears to be a later model 235.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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