Oaklyss, that number represents the rear end code for the assembly worker. My code book was printed in July of 62 for the 63 model year and this code does not appear in it so I am betting it had a running change on the rear end and the code is a little newer than my book.
Sandy, That cover will have numbers stamped in it on the right side running up and down between the to bolts. It will have a C for 3.36 gears and followed by a number. The number will be the day of year the rear end was built. You usually have to lightly sand the surface rust off to see them.