The number '56KC2313' doesn't appear to fit any Chevrolet numbering scheme i'm familure with.. not for U.S. made trucks made between 1929 and 1959, anyway.
When you enter that number into the VIN Cruncher, what it displays is basically garbage as it attempts to apply known U.S. Chevrolet Truck numbering schemes to your strange number.
In short, Garbage In, Garbage Out.
A actual 1956 truck serial number would be in the form: SSYYF000000
SS = Series, which would consist of a numerical character, followed by an alphanumeric character. Example, '4B' would be a 4400.
YY = Year, the two digit model year. In the case of a 1956, this would be a '56'
F = Factory code.
000000 = Production order number.
If your truck was a 1949 4400, your number would start with a one or two numerical character 'factory code', followed by an 'SK' (which indicates 1949 4400) then a single alpha character production month code, and then a 4 or 5 digit production sequence number.
Example: 1SKK1002
Which would indicate a truck (1) made in Flint, MI (SK) a 1949 4400, (K) in November and was the 2nd truck made that month (since production numbers started at 1001)
