[speed220mph]

My guess is the book you are all referring to is Steve Christ's HPBook "How to Rebuild Your Big-Block Ford". As you'll know from the book, C5 means it's a 1965 part. The "A" is for Ford division and "E" is for Engine & Foundry.

The suffix is the engineering change level to the casting, albeit small. Since there is an E and H change, there had to be F and G changes, which doesn't mean they made it any farther than drawings. But seeing is believing. We can see C5AE-G from the photos. Such things do slip through the cracks (pardon the pun) at big corporations, but what I think is Steve just didn't find a block with that suffix in print or on a hard part. So I think you can count on this one to be genuine. The only thing I can't tell is whether it is a top oiler or side oiler because the seller didn't say or include a right-side photo of the lower part of the block.