Sounds like fun. Good race. My old 94z28 LTI ran low to mid 14s @ 98- 100 mph stock. The have a real good punch down low. They can get off the line pretty fast if they hook up. Not as much top end as the LS1s.
About the SS vs Z28 debate. They are 99.99% identical. The SS makes amost no additional HP.
There is so little difference in an SS vs a standard Z28 it doesn't matter. I owned a heavily modded 94z28 and 99z28. I know those cars inside and out. Its totally up to the better driver. Both cars have nearly identical dyno numbers.
All you have to do is spend $150 on a whisper lid or a Direct Flow lid for a standard Z28 and it will make as much or more HP than an SS.
The SS does have some suspension upgrades but it is mostly an appearance upgrade, with a slightly better exhaust and raised airbox that does nothing. Most guys with an SS put an aftermarket exhaust and airbox(lid) on the car.
HP upgrade- I don't think so. Who in their right mind would spend 4-5k for maybe 10hp at the most. Thats it. I've seen dozens of z28s dynoed. The SS makes very little if any additional HP.
In a race SS vs standard Z28 , The better driver will win everytime.