I know the ls6 runs at 10.5, but I'm not sure about the ls2 and ls7. ls1s are 10.1 and borderline safe boost at 8lbs, so 9.7 should be 8-9lbs of boost "safely".
Ever look into turbos? I would go turbo>positive displacement blowers (roots type)>centrifugal blowers. Intercoolers are ALWAYS...