I've been having this problem for years too, but finally fixed it a few months ago. I don't necessarily recommend this procedure, was not the easiest, but I like it.
I suspected the problem was in the tank, not the dash, and this got confirmed when I swapped the whole dash for a custom and used a new Autometer gauge. I also know that it's a pain to drop the tank all the time to slightly bend the float arm while trying to get the numbers right. So, I made a nicely done access panel in the floor of the rear bed of the tub. Over about 3-4 tanks of gas and minor adjustments to the float via the new access panel, I'm good. As a start, I used a potentiometer (variable resistor, from signal line at tank to ground) so I knew exactly what ohms were needed to get the gauge to read at the 5 main points (E/.25/.50/.75/F), then played with the float assembly on the bench to get those ohm readings close. The gauge now reads dead on 'E' when I have 3 gallons left, and takes 17+ to fill. It's not dead on linear at the mid points, but it's decent.
So, I can tell you that enough playing with bending the float can make it work.
Rocky, I can tell you, because mine kept doing the exact same thing, that the filter sock on the bottom of the sending unit has come off. I have a '90 and the fuel pump has been replaced 4 times now. This last time I pressed the metal tabs that hold the sock on for a tighter fit, and I also used a couple of zip ties to make sure it doesn't fall off again.
ya know now that i think about it mine didn't have a filter sock on it when i pulled it