Which factory computer....

Excellent post by 03Ramit,

The only thing I'd add is that the 09 and later heads will bolt on to the early 03-08 blocks and do greatly increase the CR as he said, BUT if you are building a custom motor, the 09 and later heads flow much better than the 08 and earlier heads. The 03-08 Heads flow about 268 CFM while the 09 heads flow about 295 CFM.

Thus, the stock 09 heads flow nearly equal to the stock 6.1L heads and will bolt on, while the 6.1L heads can't be bolted onto the 5.7L block. Also the 09 and later heads have the same port size and shape as the 6.1L heads so you can bolt the 6.1 intake manifold directly to the 09 heads, without the use of epoxy and or gasket matching of the 5.7L heads.

But keep in mind, that as 03Ramit said, unless you dish the pistons you'll get crazy high compression.

Regards,

Joe Dokes