FE block casting numbers are located at the right rear (passenger side) behind the starter mounting location. The starter will have to be removed to see it. Not all FE blocks have casting numbers; i.e., service blocks for example. Not sure if all or just some of the service blocks were cast without numbers. Service blocks are easily identified I believe, by the vertical parallel "ribs" that are cast into the sides of the block. All of the FE blocks are cast with date codes which are located beside the
oil filter mount on the front left (driver side).
Another excellent book is:
"High Performance Ford Engine Parts Interchange"
One of these is currently for sale on Ebay...item number 180073534432, for about $16 bucks. It is a great book with tons of information about all the ford engines of the period. It has lists of all the casting numbers for blocks, heads, and most other engine parts. Excellent information to have.
Good luck, Bob