There is an earlier post on 'rest of tech' where Shadango bought a lock ring off ebay from Mainelymopars (also called Pepsparts). His post:
http://www.cuda-challenger.com/cc/index.php?topic=72598.0He mentioned the lock ring was way thicker than aftermarket. So I followed his advice and bought a lock ring from mainelymopars.
http://www.pepsparts.com/Sure enough the lock ring was 0.072 inch thick vs 0.05 thick for the previous replacement I had purchased somewhere a couple years ago. Peps lock rings was also slightly larger in diameter, and it still fit perfectly with no issues. I also bought the lock ring tool, but had to lengthen the handle to have enough torque to tighten the lock ring. If I remember right, I had bent the fuel tank lock ring tabs down in an attempt to eliminated fuel leaks at the fuel sender.
I am pleased with the thicker lock ring, which should help seal the fuel sender to the fuel tank. I have not filled the fuel tank yet, still putting the car together, but I will post the results.