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You have 3 gauges that are all reading inaccurately during warmup, then start reading accurately after 5-10 minutes? I'd look at what ties these gauges together. They all have a common harness, and a common ground. I'd start there, as it's unlikely 3 different systems would have the same issues simultaneously. I would check fuses, but don't put much stock in it as a fuse makes a circuit work, or not work, I've never known of a fuse causing an intermittent problem. Do your other gauges have issues at the same time? Tach, and speedo all good? I'd check voltage levels of your various gauge inputs at the harness during warmup and then again after they start reading correctly. Use a good known ground and measure against the ground pin in the harness, see if there's a discrepancy.
The fuel level sounds about right for these trucks, I replaced the fuel pump and sending unit in mine about 7500 miles ago, and I have the same issue. Question is, if it was reading at half a tank before you shut the truck off, does it immediately read at half a tank when you start it again in the morning? Either way, I'd definitely check the signal the gauge is getting when it's reading incorrectly vs. When it's working correctly. If the signal doesn't change, the gauge is bad, if the signal changes, then compare to a known ground vs. The ground in the harness. If those 2 readings match, then the ground isn't the issue, you've got bad information going to your gauges, test at each sending sensor to ensure it's sending the correct voltage. If they are, there's something wrong between the sensor and the harness, rewire and call it a day, if the sensor(s) is/are sending bad data, then you need to diagnose the sensor(s).
