speedo
here's the part number for a turbo 400 out of a late 80's early 90's . gm part # 12085498. it comes with two wires on it and there both grey in color. if you hold the connector with the wires pointing toward you the wire on the left will go to the speedo and the one on the right will go to ground. i would take the speed sensor with you just to make sure it matches your sensor, and ask them if they can give you a copy of the wiring diagram out of there service manuel. good luck matt