Kramer,
the casting number are located in another place on the block. My 428 block had a "S" on the back of the block. Rare 428 motor with the correct date code for a '67 GT 500. All the marking on a block can tell you something about it.
You need to order a book "High Perforamnce Ford, Engine Parts Interchange" by George Reid isbn 1-884089-33-x about $22 retail. It cover Ford engines from 221 to 460 cid. Nice book with lot of information.
Dwight
