Stopped working, hmm.. Well that is different from what tdangle reports, so you may need to make a separate thread about it if the conversation needs to get involved. But the same troubleshooting I suggest in post 5 and 6 above is what I would start with, chart your resistance curve and check grounds. Here is that thread with the chart from davepl that tdangle was probably talking about.
http://67-72chevytrucks.com/vboard/s...d.php?t=714839
Things that apply to any problem with stock gauge and sender:
1. Only the stock sender with 1/2" NPT will work with a stock gauge and it's possible to get the wrong sender like LockDoc mentions. Some folks have reported that the part number is TU5, and the part number I used is GM part number 12334869, AC Delco number G1852. Since I have a 3/8" NPT hole in my engine, I bought the 1/2" sensor and had forum member A1971Blazer turn and thread it. Other folks have had forum member Brian Mac turn and thread theirs.
2. There's a finite number of things involved that you need to check, so that is good. The sender, the wire going from the sender to the instrument cluster, the firewall connector, the cluster printed circuit, the gauge, the ground connection from instrument cluster to truck, the ground connection from engine to truck. You can check all that with an ohm meter and some wire with alligator clips.
Here are a couple more threads about the subject.
http://67-72chevytrucks.com/vboard/s...d.php?t=703388
http://67-72chevytrucks.com/vboard/s...d.php?t=627880