273 engine identification.

I don't understand the V in pishta's 63 cast block but A is 65, B is 66 and c is 67 etc. the 273 (obvious) and the 8-5 is the assembly date. August 7th I just found series numbers in the back of the Galen part number book. S=1962 T=1963, V=1964, a=1965, B=1966 etc.
OK, mystery solved.....V is my 64 model year but its a 63 casting...So what is -I2-7 if my casting date is 11/20?