Back in 1940, many states including Texas titled vehicles with the engine number. When someone repowered with a replacement engine from GMC, it came with the first three digits stamped which denotes the displacement, and then the installer stamped the rest of the numbers to match the title. My guess is in your case, your vehicle would have had a 228 and the engine would have started with 228. Meanwhile someone with a larger truck that came with a 248 purchased a GMC replacement engine, but chose to replace the 248 with a 270. GM stamped the replacement engine with 270, but the installer stamped the 248 number on it to match the trucks title. Then at some point in time the truck that originally came with a 248 was salvaged. The guy who owned your 3/4 ton pickup need an engine and he bought the 270 out of the salvaged truck that originally had a 248. The 2135412 is a block casting number and it denotes a 270 cast between 1946 and 1952.
What number is used for a VIN on your title. If it was titled by engine number, it would probably be something starting with A228 or B228.
