Shouldn't the head and block be of the same year ? Is this head special in any way ?
The block casting number is from when part was engineered so it only gets you close to a range of possible years. To know the true year of your engine and head and any other casting you need to look for the actual casting date this will give you exact day that it was cast! The casting date's will look something like this "6M08" on what looks like a small tag cast into part.