I have not made any real progress on the truck, since getting most of the fuel system removed. I still have one rusty steel line to remove from the frame, but it parallels the brake line that I need to replace, so I'll remove them at the same time.
Since getting the tank removed, I have run the engine once. I hooked up a fuel line and filter to the pump and ran it straight into a can of clean gas. I can't drive it this way, but at least I can keep the truck running and starting.
I also made a few calls about getting the tank cleaned and sealed. There are a couple of radiator shops here in town that can do it. $75 to get it cleaned and another $75 to seal it seems to be the going rate. Unfortunately, all of these shops are on the far side of town, 20 miles or so from here. Eventually I'll have to make a special trip down there to drop off the tank.