Here's my 2 cents worth from my own experience with crusty fuel lines.
"If in doubt, replace it all".
A new tank is not that expensive. Buy the Spectra Premium F32A, Dorman 692232 sending unit, (I used) Delphi MF0007 fuel pump, all from Rock Auto. The 3/8 SS line I bought from NPD. Rubber tubing needs to be Fuel Injector grade hose as it is ethanol resistant (inside). PLEASE make sure to use the correct fuel line clamps,
NEVER worm gear clamps.
Here's a pic of my old rusty line which actually broke in two when it was removed.
There has been many post on this subject if you care to search.