I wonder if these are from ATK? Summit sells a 6.0 LQ4/9 block that is .030" over and supposedly finish machined that they get straight from ATK. Those blocks are seasong (used) blocks that have been cleaned and bored.
Here is the listing for the 6.0 block:
http://www.summitracing.com/parts/SUM-150105/
Here is a thread on ls1tech detailing the 6.0 block:
http://ls1tech.com/forums/generation...-ls-block.html
There were som naysayers in that thread but overall it seemed like most were pleased.