L92 Head on LS2 Question.

First post but here goes. I have a 2006 vette with the LS2 motor and read about the L92 heads in this article.
http://www.gmhightechperformance.com/tech/0702gm_ls2_engine_l92_heads/index.html

What I don't understand is how it doesn't mention anywhere if the L92 heads were milled back to 64cc combustion chamber size.

If you go from 64cc to 70cc don't you change the compression from 10.8:1 down to 9.9:1? Are these heads really just bolt on and go.

I would have thought you'd have to mill the heads (then change to shorter push rods etc.) to make the swap work.

Can you really see increase in power although you drop your compression?  

That is an issue.  You can only really mill the heads ~.040 (for thickness and intake fit)  which will take them to about 64ccs.
Beyond that thinner gaskets will help.
In my case I figured I would need shorter pushrods but actually measured out to 7.4 for .100 preload.  
2000 C5 with LS2 402, L92 heads