OK, I'll try to answer in ballpark figures you'll need to know... there are approximates and rounded numbers, which will also compensate for misc parts you'll need to find along the way
average price of LS1/t56 combo with low miles - $4500
JCI install kit + headers + driveshaft -$800
Belts, pulleys, hoses - $200
JTR radiator, vent T, and intake ducting kit - $450
custom welded exhaust, let's assume dual with X pipe, all parts provided by exhaust shop - $700
R200 diff, mustache bar - $100
If you're doing the harness yourself, you're saving a nice chunk. ECU reprogramming - $200 (vats, egr, o2 sensors, smog, speed governor)
Assuming you'll use a stock tank, you'll need a weld in AN adapter plate. Boiling tank, welding it on, cost of part, recoating/repainting - $300. Or you can get a camaro gas tank w/ pump (ie. i'm selling mine for $225).
Fuel lines, adapters, corvette pressure filter modification - $150.
Taurus 2 speed fan - $75
So far, this is at $7425. Not counting suspension, brakes, etc if you are planning on doing those.
In my case, I bought a running '02 camaro with 26,000 miles that was poorly damaged for $4700, stripped it, sold $800 worth of parts from it so far. So my LS1 (with LS6 intake manifold for that year) cost me $3900. I had most of the stuff already from over the years. I still have some camaro parts to sell off, basically if I get a grand for the parts, my motor/trans cost me $3700, and I'm happy with that number.
If you look at 240zprace's post about dyno numbers, he dynoed 346 STOCK to the wheels. only thing about his car was an ECU cleanup/tune. Don't forget that you lose the power steering, AC, smog stuff, exhaust restriction (camaros had 2 catalytic converters, really poorly designed exhaust, see pic below... you can see the flat Y pipe on one side)
This is why when people upgrade to true dual exhaust on fbodies, they see enormous power gains.