I can give you some advice here seeing how I just sold my 1999 SS.
With the LS1 it gives you allot of bang for the buck. For instance. I installed a whisper lid, K&N filter, a MAC offroad y-pipe with O2 sims, and cut the EGR sensor out of the TB. Before these simple and inexpensive MODS it dyno'd out at 292 RWHP 321 FWHP after it was 333 RWHP and 370 FWHP. I spent a grand total of about $550. Quickest time at the Gainsville Raceway was 12.989 at 114mph best of three runs. No not street tires. With a few more mods and little more money the potential for power was very real.
I just sold the car for $18,500 and it was in excellent shape. Expect to pay between $18,000 and $22,000 for a good LS1 powered T/A or Camaro.
Okay now I'm sick all over again
I want it back.
Hope this helps