Recently I bought a T-56 from a 1993 Z28. The trans has 33k on it. The previous owner at his first time to the track broke the ouput shaft in the burnout box. The shifter still moves freely, so nothing internal is locked up. Just needs the Output shaft replaced. You can get a factory shaft for under $150, or get a Hardened Viper Shaft for $299 and have a nearly indestructable T-56. Get a crossmember, and clutch and you have the entire setup..... Included with the setup is:

Transmission with only 33K
Stock Shifter
NEW GM HYDRAULICS (less than 2k on them)
Flywheel
Bellhousing
Pedals
Check Plate
Steel Driveshaft

$1100 OBO