OK, I called around to every radiator shop along 270 and got lots of "nope, we don't do that", "you mean oil pan" (no, I mean oil tank), and "what the hell is an oil tank" type responses. So I decided to clean the damn thing myself.
After a lot of scrubbing, 99% of the crud if off the outside. And so is about 50% of the paint. This is how much paint is gone from 20yrs of use - I didn't sand or wire wheel this.
So here it is sitting for the next day or so, completely filled with about 4 gallons of kerosene. I used part of the old oil lines to help block off the holes, and made a little block off plate to cover the hole left after removing the sender:
After this soaks for a while, I plan to drain and prep the tank for a coat of POR15. Once prep'd, I plan to pressure wash and soak again, this time using acetone to remove any kerosene and other residue. Then paint, flush with some oil, and reinstall.
I also plan to take care of some of the surface rust that started forming in the rear of the car where the tank is mounted:
You can see it just about the filler neck/filter access hole. Good times. Time for a shower - a day spent with lots of different chemical degreasers has left me a few brain cells lighter and smelling to high heaven.