It was common to use the engine serial number for title purposes when those trucks were new. I have two 1952 Chevy trucks with the same problem - the titles used the engine number. There was no standard VIN format then, and state DMVs all did their own thing. Obviously this is a problem when the engine is replaced.
When I went in to get a title for my 1922 Ford speedster the clerk said the vin was supposed to have 17 numbers, next supervisor didn't know what to do and the third level agreed the the engine number was used for title and I got my paperwork . I bought a 46 chevy truck, got a statement of facts form the widow , the sherrif deputy inspected the truck and used the body tag for the title
I have an Idaho title for my Model A roadster that is not running, I got a letter from the DMV asking if I still owned the car because someone was trying to register a model A pickup with the same engine number. I called and asked if the DMV had inspected the pickup and verified the engine number. he said he had. I said that my engine was swapped for a later engine and I assumed my old engine was junked. and that the title was not changed to match the V8 by previous owners, I said that Since my roadster was not stock I agreed to get an assigned number as long as it stated the year was correct, I have since found a better frame with a matching bill of sale and need to get the paperwork to have an original title to match my new frame