The sender out of the car should read about 8 ohms to 86 or so as you change the float level. Just use your meter and put one wire on the tube anywhere and the other on the terminal. Just a rheostat.

Finally dropped the tank on mine the other day and found that the float was sticking against the stock and not letting it move. I don't know why I didn't check this before I put it in. I did check that the rheostat was working but didn't pay attention to it slightly snagging at the bottom. Drats!

Now I am waiting on a new tube seal to come since I destroyed the brand new one taking it out.

The other gauges in the aforementioned thread seem to be working correctly now and I have done nothing. I guess it was just 30 years of sitting..