After some research I beleave that the engine was changed by the milatary with an engine out of there spare parts.

Can anyone shed some light on my recently uncovered engine number? It reads "US.24-7596". I believe it's military due to the two bolt oil fill pipe flange but the number prefix is not like any other I've seen described. Thanks in advance! I also have that code on the block of my 1951 m37 ...