1) Replace the fuel sending unit.
2) Replace the sending unit retainer seal. You should be ok to reuse the metal retainer itself.
3) Replace the filler neck to gas tank grommet.
4) Replace the filler neck to trunk floor seal.
5) Replace fuel pump, any non metal fuel line.
6) Rebuild carb(s).
Basically anything non metal has lost it's 'integrity' after 20 years. 'Wag', my 73, had an unknown history when bought in '03. When water was found in the gas, i dropped the tank and discovered jb-weld on top of the tank had deteriorated and was letting moisture in. I replaced every component from the fuel system except the filler neck. Overkill? Yes but i won't have fuel system issues any time soon.
Russ