In my opinion, just looking at the only the stampings, they are fairly convincing.
Always use as much information as you can when evaluating a block and have the pad cleaned off - no paint or corrosion. Look at the font and spacing. Also look for broach marks, the block casting number and block casting date if possible. Deck height and the complete block to head mounting surface may need to be scrutinized (head off the block) in some cases.