[jorgensensc]

These are the facts as I know them:
I did a blazer tank swap on my truck and the sending unit sends the same ohms. My guage wasn't working correctly( as I'm pretty sure your's isn't either), and was broken. i bought a good used one from someone on the board and bought a new resistor (white thing on back over the two posts), filled the gas tank up and hooked the gauge up. i used a fork to remove the needle, set it to full (be sure you are not on a driveway with a slant, I had to do it again on a flat surface, Doh), then ground the fuel sending wire going to the gauge (sends the needle to past empty). Then connect it to the sending unit again and make sure it goes back to full. Do this a couple of times to make sure the gauge works correctly before putting everything back together. I did all this using long wire jumpers with alligator clips, so the gauge wasn't actually installed until I was finished. I cannot stress this enough... MAKE SURE ALL YOUR GROUNDS ARE GOOD!!!! make sure the tank is grounded to the frame, and make sure your gauges are grounded good. If you have a partial ground you will fight this all day long.
Sorry to be long winded, but I speak from experience. It took me the better part 6 months to finally get all my gauges restored and working properly. Finally they ALL work like they should. Hope this helps a little.
Shawn