coming back to finish the thread.
I got it all to work. I fixed the gauge reading 1/4 tank by putting the "Runtz" resister on the back of the gauge.
To fix the needle jumping,,, the new sending unit had to be replaced. I could feel the break in the sending unit as I worked the lever. We hooked it back up outside the tank and watched the gauge needle when the sender went across the break, it flipped back to "e".
Roberts replaced the sending unit, but told me it was my fault. He says that when you tighten up the screw holding the wire on top,,,,if you tighten the screw too tight, you break the sending unit and cause the needle flip. I did have the screw tight because ,,,,well,,,,I hate loose stuff. Maybe it was my fault? Beware ,,and just snug the wire I guess. Seems awful fragile,,,I only used a screwdriver.
I made a tool to take out the sending unit from the access hole in the cab. That worked out well. I learned that when you put the old sending unit in and using the old retainer ring,,,if they both are rusty or rough, it may grab and turn the sending unit as you are tightening the ring, bending the tab. A dab of grease smeared around the bottom of the retaining ring cures this.
I drove around last night trying to waste some fuel.....just so I could see my gauge work! Really the only thing I did was find out I have a really hot heater! That baby can run you out or make you roll the window down! It isn't real cold yet though,,,,,,