I don't mess with old tanks. I have quite a few old GMC's I buy reproductions for $119 and another $40 to ship them to Texas. It is very difficult to get all the lead and rust residue out. There is either an elbow or a petcock right under the tank. That is usually where the trash collects. There is a drain at that point where you can usually drain the trash out, but I don't like the idea of getting under a pickup and have stale gas running down my arm. That Is why replace the tank and it takes an about an hour to do.