There are couple of different codes to determine the rear the codes here are the codes for a 10 bolt 8.2" EDF 21ST WHICH IS GEARED 2.73:1 & DOWN
EDB30116 WHICH IS 3.08:1 &UP
then codes for a 10 bolt 8.5" 410409n 2.56:1 &down
Then the 12th bolt codes are ed32088 2.73:1& down
30140pm1 3.08:1 to3.73:1
Ed30174 3.90:1& up
A bit late to the party, as King hasn't been around for about 5 years, but I noticed everyone seemed to interpret is question as wanting to decipher gear ratio of the differential, but I didn't read it that way.The casting number on the front is gbg1402, what does this mean, couldn't get a clear answer on internet.