Toyota :: 1987 - Fuel And Temperature Gauge Won't Working Suddenly

I borrowed a friend's small Toyota truck for a few days of easy chores, and made a point to check the fuel at the beginning: the gauge showed 3/4 full. Four days and only 25 miles later, when I got in to return it, I noticed the fuel gauge was not working, I'm certain there's no fuel leak, I would have noticed that: the truck had been parked on my property the entire time, driven only a few hundred feet from one spot to another moving firewood around, so I would have smelled the gas if there was a leak.

When I added a couple gallons of fuel, the gauge didn't budge. Once on the road, I realized that the engine temperature gauge was also dead - no change on the gauge after 10 miles. So I have two non-functioning gauges which failed on my watch. This may not be directly my fault, but as my friend is kind enough to lend the truck whenever I need it, my contribution is to provide maintenance.

Is there anything in common between the two gauges which would explain the synchronized failure? Or is this total coincidence? This one is outside my experience, so don't know where to start. It's a 4 cylinder, 5 speed manual, base model truck, about 150k, generally runs just fine. There are no other gauges, and I don't recall what warning lights there might be, but I didn't see any after I realized there was a problem. Would the whole instrument cluster die at once, or could this be something like a bad ground for the cluster? I don't mind investing effort into tracking down and solving a problem, but if it needs a new cluster, that will cost more than I'd like to contribute, yet the problem occurred while I was using the truck (gently). My total use of this truck for all the times I've borrowed it is certainly less than 300 miles, so I'm reluctant to fund the entire repair if this is something that just comes with age.