when I had my 59 Suburban, I ended up buying a sending unit for a pickup and using parts of it to repair my original one. You might try a universal/adjustable one,
http://www.americanclassic.com/ has some that may work. They only fit in one way and are a pain to get exactly right. As far as the tank, I have not seen direct replacements but, I did not look very hard as mine was fine.
