New Gas Tank Sending Unit Leaks

I just found my old lock ring. I had pitched in the trash can. Fortunatly it was still there. This proves that old adage that you should never throw your old parts away. I will give the old lock ring a try a let you guys know how it turns out. Thank you very much!

Would be interesting to know the relevant size differences of the new and old lock rings.

Maybe a few spots of weld and a grind could help the new rings seal?