If you take a look at this page 1952 Chevrolet Truck Data
] from the GM Heritage Center site, the "BKCA" indicator was used for the "engine serial# identification" (see the extracted screen shot below).
Your trucks original ID should have started with a 1 or 2 digit "number" (for the Plant), followed by the letters "KP" (3100 designation), then a single letter to indicate the "month" built and finally the unit sequence number on the Identification Plate.
It would help if you could post a picture of your ID plate to see if we can help with further details.
On a related note, it is possible that sometime in the past, the ID plate may have been changed to reflect the "engine serial#" to be the vehicle ID # as that was quite often used for titling and registration in some states instead of the original truck ID number.
Hope this is helpful.