Take all the screws out that hold the cluster in, start the truck, rough up the cluster a tad bit and see if anything comes on.
When I bought my 88 the only things that worked was speedo and oil pressure.
Check all the plugs on the back, clean them up a tad. You can replace just the gauge if you dot want to loose the original odometer.
Also check where the gauges set into the cluster. The little tabs get weak and won't hold a steady connection. You can try to bend them back or add a little solider to the posts to fatten them up