Sean, 98 -00 are the weaker stock ls1's, while the 01 and 02's where the big dogs.
01 02's had the ls6 manifold and about 25% where actually ls6 blocks. These motors dyno consistantly in the 335 rwhp range with only a lid and exhaust upgrade.

Also, the z06 will just feel faster no matter what, as it is sucha well designed, purpose built machine. But, with just a heads/cam upgrade on a F body, you can make MUCH more power than the 405 crank hp GM puts in the Z06.

If I were you, with budget being somewhat of a concern, go spend 8k on a z28 auto, add a cam, a stall and some spray...and look out.