I just had my gas tank of 79 years boiled out and when the shop finished it they put in one gallon of diesel and swished it around. Then dumped it. I reinstalled in on my old car and so far everything is doing fine. I do have a glass bowl type filter and it is still clear. Take it to a Radiator Shop who has a tank to dip it. For me it was $68.00 here in the Sacramento area. He pressure tested it also for five lbs.
Normbc9