My block is C6 FE 6015A, but my heads say 289, the number 64, and a cast number inside, 4C24, and a stamped number outside, 12873, are these anything special?
Date/year cast number is between pushrods on valley side of heads on number 1&8 cyls, you will need a mirror to read- remember 9 will look like 6 & vice versa.
