Rebuilding LS aluminum blocks is frequently not cost effective, because there's so little room to overbore. If you have to re-sleeve, you're better off with a crate engine, or having one built from scratch. I had a forged LQ9 (iron block LS1) built by Erik Koenig in Houston. The iron is better suited to supercharged and high power applications, as there is significantly less cylinder wall balooning and squirming of the deck. The bare blocks go for about $700. The trick is getting a controller and harness if you're going the EFI route. Otherwise, a carburetor perched on top of a Whipple is pretty slick, too.
You don't need to go low on compression, as you might with a turbocharger. Positive displacement blowers like Whipple and Eaton are very happy with 10-10.5:1 compression with premium fuel, leaving you with something that's not a pig out of boost. Whipple blowers are VERY predictable, as the relationship between boost and RPM holds no surprises.