The first 400 block I built, assembled, for a customer who had all the machine work done and all the parts ready for assembly, he assured me that he had that block magged and sonic tested before having it bored and hon with a torque plate and the same type head gaskets.
it split the number 1 or #3 (CRS ) cylinder wall on the cam side of that cylinder on the second dyno pull, it turned out that we couldn't fix that block with sleeves due to that side of cylinder walls were all less than .040 thich and the sleeves wouldn't seal at the bottom of the cylinders ,
He had it bored to 4.375.
I now use a minimum of .160 cylinder wall thickness as my minimum after boring and honing on both thrust surfaces, .120 minimum on the non thrust sides

A friend of mine sold a 400 block to a guy, so a couple of weeks ago he brought it to me to sonic test. The moral of the story is don't sell a block without sonic testing it first because if he had he wouldn't have sold it. This is after final hone to 4.375".