Runco don't tend to publish exactly which chip so you probably won't get a definitive answer on this. You should definitely demo the LS-10 and take some Blu-Rays with dark scenes to the demo and see if the black level is OK for you. I doubt you will be dissappointed by it.
However, if you can find one, I'd try to hunt around for SIm2 Lumis Uno demo. The Lumis range all use 0.95" DC4 chips so the native contrast will be better than the 0.67" DC3 chips (probably what the LS-10 uses...) Plus, you get the other advantages of the larger chip size. I have seen at least one Uno advertised for under $20k. And if you don't need the lumens then the Sim2 M150 is definitely worth a demo (probably easier to find too), again uses the 0.95" DC4 chip and produces a fantastic picture.