No fuses for the gauges. But a there is probably a fuse for the wire that brinks the (+) reference to the cluster for the multi pin connector. EDIT, fuse is 3 amp at the bottom right of the fuse panel, labelled trans kickdown on the 1978 manual with glass fuses,, I suspect that the 1980 has the same configuration. I do not have a clear print of the later manual at the moment, 1980 being a flip year and the vehicle being down under, it is a bit of a challenge to be sure of what is your configuration, what transmission TF727 or TH400 with the quadratrack 1339 or quadratrack NP version that was on our production year in the US!
Do you have glass fuse of the plastic colored embedded fuses?
As said above, the gauges are powered by the voltage regulator - a crude winding to lower 12v to 5 volts- housed in the coolant gauge . All the senders for the gauges rely on ground resistance as referenced to the battery/engine ground.
A search here will give you some good links and a way to build a dedicated tester
http://www.fsjnetwork.com/forum/viewtopic.php?t=9404
Page 3-47 here:
http://oljeep.com/gw/74_tsm/3-Electrica ... End%29.pdf Step-by-step instructions. (link provided by Tim)
a ground wire in the back of the instrument cluster can be added, and the pins on the back of the cluster can be loose and be resoldered by a quick application of solder to reinforce the pin(s)
If you are up to it you can remanufacture a voltage regulator for a reliable/constant voltage
http://www.fsjnetwork.com/forum/viewtopic.php?t=8334
cluster feed for the glass fuse here