Factory cast iron late model block. Interesting thing about the 460 blocks is they made them all the way until 1997. And the blocks cast during the 90's have longer cylinder walls which make them better for strokers. Late model 460 blocks are still fairly easy to find since they made so many of them. Lots easier to find than a good B or RB block. The 460 block is also really strong. We're planning to make 850 hp with this engine and the block doesn't need any prep other than ARP main studs and proper machine work.