Shows as 94-06.... likely will not work on the '06 Duramax with the 32 bit data bus.never used one, but here it is, summit sells it for aroud 140.00 if I remember right
http://www.granatellimotorsports.com/granspeedo.htm
May or may not be 100% of what you want.Thanks Guys,
Contacted Tech Support at Granatelli. They say so long as the vehicle has a "Vehicle Speed Sensor" wire between the speedo and the computer,