Put a pro-shifted T56 in one and see what it does.
The guy's at T56 rebuilds run an 02 Z28 that has been lightened up some, heads/cam/full boltons and its running in the low 10s. I've seen it run at Atlanta dragway and the car is a beast. Makes me wonder what a ZL1 or Dick Harrell car would do with one of their transmissions??? Here is an in car video of the T56 rebuilds car.
http://www.ls1tech.com/videos/T56Rebuilds.wmv