ok, generally you want an absolute minimum cylinder wall thickness, on a stock production block of .180 and .230 or thicker is generally considered to be ideal, anytime your bore reduces the cylinder wall thickness below .200 in my opinion, if you intend to race the engine, you should fill the block to the lower freeze plugs with a block coolant passage filler to reduce the unsupported cylinder walls tendency to flex, which reduces ring seal., and generally the semi-safe limit, with the block filled is at about .200-.180, below that, wall thickness, becomes a potential major problem and the blocks life expectancy, is usually lower,
Id reject a block as a race engine if the upper cylinder wall thickness is under about .145" as an absolute minimum,and only go below .180 if that thin wall area is supported by block fill now Im sure youll find guys who have raced thinner cylinder wall thickness, but its pushing your luck.