This is the adapter/spacer you need. Don't get the bolts they have listed, they are too short. Just go to your GM dealer and get the bolts for a 2002 chevy truck with the 6.0 motor.

http://www.summitracing.com/parts/NAL-12563532/

I had to put my spacer between the torque converter and the flywheel. I have the 5.3 flywheel that is curved.