Well I'm about 6k worth of parts for mine. That doesn't include exhaust, wiring, driveshaft. The parts you need are decided by the parts you get from your LS1 combo. But basically you'll need the motor, trans, Broken Kitty trans/motor mounts, radiator, wiring harness, driveshaft, headers/exhaust, fuel system of some sort. It all adds up quick, it also depends if you are going to upgrade anything else, suspension, rear-end, guages, etc. etc. There isn't a definite answer for what does it cost, its all based on what you can afford and what you have. Just search a little more there is a long running thread of "how much did it cost" you should check it out.
Tyson