I know this topic has been worked over but there seems to be some contradictory information in the threads I have seen. Can anyone clarify which block, the LS1 or the LS6, has the nickle sized circle embossings on the passenger side at the top and bottom of the head? Thanks.

 

from PSJ:

12561168 is the block number, From under the car....On the driver side rear, where the head meets the block you will see the casting number

 

The LS-1 engine has the embossing circles. The LS-6 does not.