Found this here on ls1tech about variances in LS2 deck heights by ChucksZ06 back in 2006 http://www.ls1tech.com/forums/ls1-do.../t-543708.html
"My first ls2 block with 4" eagle crank and rods was .005 in the hole. I am now doing an ls2 block with a stock crank and 6.125 rods( same length as 402 build), same piston manufacturer and the pistons are .008 out. I think the stroke on the 4" crank was not quite right. So from my experience you pretty much have to mock up the parts or it is guessing. Good luck."
Keeping the top ring below deck seems like common sense. It's common for the crevice height (top of piston to top of top ring) on performance pistons to range from about 0.180 - 0.320". So presuming (what I consider) a loose quench of 0.035" and super tall 0.125" gasket you should still be safe with low crevice volume pistons all the way down to a crevice height of 0.160". Still that's a little too close if you're running a low crevice height pistons near 0.180".
9.240" Deck height
2.000" less 4" stroke/2
1.115" less my manley piston's compression height (was designed for a 6.125" rod)
6.200" less my lube-tube oliver pistons
puts me 0.075" out of the hole.
for a tight 0.030" quench I'd need a custom 0.105" thick gasket.
I also found Lingenfelters book on google. He mentions that he reccomends 0.250 crevice height for street engines, but has seen all the way down to 0.100" on all out N/A drag engines!
John Lingenfelter on modifying small-block Chevy engines: high performance ...
By John Lingenfelter http://books.google.com/books?id=GUC...height&f=false