Jeff - I'm not much help here, but here are my thoughts. I'm not sure if they were available for a Chevrolet of that vintage. It does seem like it would be difficult to retrofit those as they get wired into the entire wiring harness.

A visit to the local Chevy dealer should answer your question. Chris is correct about the wiring. I had a 2013 Charger that came without a compass which I wanted. I asked the dealer what it would cost to add one and was told it's not possible (at least not for a reasonable cost). Car companies are so big into option "packages" that it can make it difficult to add things. In my case, adding a compass would have required adding a whole new sensor package.