the block you are refering to has the casting # DOVE. This block is the same type as the 2 bolt 429 CJ. I have found these blocks were used in marine applications, along with the spot faced CJ type rods. It is the best 2 bolt block to use if you can find one. I would recomend sonic checking though because the last DOVE block I had could only be bored .030 safely. The sonic check mapping showed the cylinders were thick at the bottom of the bore but thin at the top. Sort of the opposite of what you would want.
HTH,
Mike