I would check for a fuse. I believe you should have the elect dash panel so you may have to pull the cluster to check to make sure the harness is connected properly. If that still doesn't help you may need a new cluster.
I may be a little off on this, but i thought the speedo in an 89 was gear driven.
My recent experience is with an 89 F250 4WD 5 speed. I bought the speed sensor that you linked to. And I bought a new gear because mine had enough wear that it would jump a bit. My REAL problem turned out to be a slightly elongated speedo drive cable.
I took off the 11mm retaining nut from the speed sensor and pulled it from the transfer case. I could turn the gear, but there was a lot of resistance. Then I pulled the cable from the speed sensor. The gear/speed sensor assembly now turned freely, AND the cable now turned freely. Stuck them back together. Resistance. Pulled apart. Free spinning. So I took a 4.5" angle grinder and took a small amount off the cable. I kept putting it back together and turning it, then took a little more off until it all turned freely. I put it all back together and now my speedo works flawlessly.
Good luck with yours. And be aware that the speed sensor/speedo cable changed places and functions a few times around 89.
Thanks for the replies! I believe I figured out the cable I originally thought was the speedo, is actually a hydraulic clutch. The PO told me it didn't have hydro clutch.
The gas gauge, tach, and battery gauge definitely work. The coolant temp, and oil pressure MAY work, but they always seem to be stuck around the same spot. The speedo is just at 0.
I had to replace a heater hose pipe because it rusted through. When I was putting it back the water outlet pipe cracked in half. My only option was to get a new outlet, hardware store fittings, and put the temp gauge AFTER the thermostat on the way to the rad. This would only mean I would have to wait for the thermostat to open before getting a temp reading. I hope I didn't confuse anyone.
I'm going to go check the rear end to see where the wires go to and the t case as well wish me luck