I've only had my car on a dyno once in the past twenty two years that I've owned it, and the results were unimpressive. But I've seen a careful tuning of modified LT5's a couple of times, and it was a phenomenal improvement in overall performance.
From what I've observed, a good tuner can tweak more performance out of an LT5, in a half day of tuning, than any one modification available. And when many small mods are made, headers, intake improvements, etc., dyno tuning is essential to get the best response from what you've paid for.
I don't quite understand the concern stated above about blowing up your ZR-1 on the dyno..you've got to be kidding. To me, a dyno run is no more destructive to a relatively stock LT5 engine that a spirited run through the gears (to redline) on your favorite "exercise " road. And that happens to my car virtually every time out.
And remember the GM test cycle that LT5's were exposed to. Constantly running a motor from torque peak to redline, and back, over a long period of time. Then a teardown that showed virtually NO wear.
I think some folks have watched too many episodes of "Street Outlaws", where engines are run on the ragged edge of detonation every time out
The best dyno I've seen is the drag strip. Your trap speed is a practical demo of actual applicable horsepower. I figured, (and I could be wrong), that my 117mph trap speed was equal to about 420hp. at the crank. And that's pretty solid for a stock 375hp. LT5 with no internal mods whatsoever. Bone stock except for exhaust.