From experience I can tell you that Block filler (HardBlock) will not prevent water from weeping through those cracks. If you plan on filling no matter what, then I would pin the ends and used wicking grade Loctite on the cracks. This has worked and held pressure in similar attempts.
I agree with the above. I had a 440 block with similar cracks I filled the block with the Moroso block filler past the cracks and it still seeped. Another alt. is to use loc&stich pins. I have used them several times with success.
