Hi Hi Pro, I have bean reading about 3956618 SBC Blocks on your forum. I have one that is bored out to 40 thou. and been decked. It is a 1969 block and has the nodular iron 4 bolt caps on it. On the opposite side to the engine number on the block is an unusual cast symbol that looks like a type of Fuilie or castle symbol. Can I send a Picture of it to you. Your help would be greatly appreciated. thanks HT Monaro.