FWIW, I believe the H 9 6 is the date code (August 9th 1966). My third birthday, coincidentally. The GF code was the same for 1966 also.
a more detailed: build date this number is STAMPED: V0812GF = V=flint mich., 08=August, 12=day of the month, GF='65 '66 '67 283 p/g casting number, this number is a raised number at time of casting: 3896944 works out to 283 this is the CASTING DATE, raised number at time of casting: H96 = H=August, 9=9th day of the month, 6=year this block was cast on the 9th and built (assembled) on the 12th, as a 283 destined for a powerglide trans in a big body car. yeah, i know this is old info, but so many people get it wrong STILL, i just wanted to show the correct info so when somebody sees this there is no question.