It depends on the year of manufacture of the block. Somewhere around the middle 1980s, GM started making blocks with thin wall castings. Those engines could be rebored to .030" oversize without any problems. Earlier blocks from the late1960s and 1970s could handle a 60 overbore. There will be a casting date somewhere on the block. If only one or two cylinders have deep pits, repair sleeves can be installed, but the parts and labor cost gets impractical pretty quickly, especially since a 350 is a "belly button" engine- - - - -"Everybody's got one!" It's easier and simpler to fund a better condition block than shoveling money down a bottomless pit!
Jerry
