Hello, I'm new to this site and look forward to anyone's input. I have a 1961 chevy step side that is sitting on what I believe to be a K5 blazer frame. I need help decoding the VIN# I found on the drivers side door frame. I've been searching everywhere but cannot fully decode it. The VIN # is 1C853S120790. I know the 1st digit is the year 1961 and the 2nd digit "C" is for a 2 wheel drive, but I cannot figure out the 3rd, 4th & 5th digits? The 6th digit is an "S" for St. Louis... I appreciate any help I can get to figure out the 3rd, 4th & 5th digits. Thanks!!