Why are you concerned so much about wall thickness? At .030 , your wall thickness is not the primary area of concern for durability on an rb block. Many high hp .030 combos eventually beat the main caps out first. A .030 in various dish 440 combo piston is readily available. I also know first hand that getting a straight bore from a stock block at .010 or .020 in all 8 holes you would be lucky at best. Just my