Turbo or blower, I'd get that compression lowered. We've built a couple of blower setups on top of stock LS6 motors (10.5 compression), and max power was seriously limited by the amount of timing we could use before hitting knock retard. With ~6 PSI boost, we were hitting knock retard at just 9 degrees advance at max volumetric efficiency (in the 3500-4500 RPM range). Just my opinion, I'd shoot for about 9.5 (which, incidentally, is about where the LSA and LS9 are).
That brings up another point, which is that I'd use an ECU which has provision for knock sensing, like a GM, Mast, or Holley. Detonation can destroy a boosted motor very quickly, and you don't want to worry about a tank of bad gas causing 5 digit rebuild costs. With knock sensing, you can tune less conservatively and still be more protected.
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