340 blocks
When you buy a 340, you are basically getting a 360 cylinder core already bored .040 over. Im sure the core shift has been more pronounced in these thinner blocks as well. Plus you know all of them have been run hard in their past lives, why anyone would have bought a 340 and not flogged it is beyond human nature. If I was a betting man, I would shoot for a 68-70 block if at all possible. There is a T/A that needs a cylinder sleeved somewhere here or "there" for $400..?