3.597 with a final bore of 3.622 was one size we were throwing around, but were going with the 3.591 as the final bore size. Not sure what are rough bore size is right now but it's within .010 of the final bore size. The cylinders were sonic checked and nothing is less than .220. My eyes must be deceiving me because it sure can look thinner if view from the right angle. The point between the water pump side you can get a finger on each side and view it from the top. I'd swear that I can feel my finger prints there. We checked calibration on the sonic checker a few times. Even sliped a piece of metal behind the wall to see if the reading would change. (I case we were also reading the next cylinders thinkness too) No change.
Were going with the 4.25 stroke for a final displacment of 258.25. A little disapointing that its not 260 or bigger but with the 258 I get a dyno warranty.