On my .030 440, the old Mopar Performance Engines book had me paranoid about thin wall blocks since the block I used was a 78. It passed sonic check no problem. I can't recall how thick the walls were, but the machine shop said for mine, that .060 over on that block wouldn't have been an issue. Also the majority of BBM blocks they had tested were thin at .030, no matter what the casting date was. I was prepared to go and buy blocks of all different vintages, guess it doesn't matter.