During one of my winter projects I was tracing a tail light problem (bad connection). Turns out it was the intermediate harness. It was brittle and the wires were almost broken completely in a few spots. Of course it's not available,(the Vista harness about 2-3 feet longer than the Cutlass harness) so you must improvise. I bought a Cutlass Harness and used the first 2 feet. made a splice under the seat area with the harness I made.
Bought a 6 wire harness connector and made the new hook up with the tail light harness in the spare tire well.
Guess what, everything works now! Pictures will summarize the task. Another relative easy but time consuming job.

Here's the Cutlass harness (Bought from OPG) plugged into dash harness. I used the first 2 feet and made a splice under seat area



used 14ga wire trying to match factory colors

Made splice under seat area

Routing harness along floor pan

Made connection with tail light harness using a new connector

 

Nice work!