I completed the install of the 1990 Burb cluster in my 1979 Chevy Silverado. I traced the harness on back of each cluster and re-pinned the connector to match the 90 cluster. It took a couple hours to get everything in the right place, but now all the gauges and the speedometer work.

I took pics of everything before I made any changes so I could reverse the process if I could not get things to work.

Thanks for all the feedback for help.