Thanks, ok don' t do all the work for me, if you want I can help you.
For the Chevy Tahoe Z71 2001
In the green/white wire of the radio harness, and the green/white wire of the cluster harnees ( pos A3 ) you can find the speed signal ( VSS ), and for the reverse signal the geen wire off the conector of the center instrument panel utility block located under the instrument panel on the left side of the steering column.
Hope it helps