Are all 340 blocks the same?

The T/A block would be great but I'm sure the cost would be a deal breaker, I would shell out the bucks for a race block if I could afford it. I'm reasonably sure I will exceed the limits with a 360 block, that's why I'd rather have a 340 block, I'm not going 340 block for the bore. I have seen a few 340 blocks pop up in classified adds, usually around $500 so I view them as still being a pretty good deal. I'm in no rush so time is on my side, I can wait for the right deal. Thanks for the info, I now know the casting date does not matter.