Old fuel tanks and cans can be a bit of a bear, but they can be repaired.
Depending upon how bad the interior is, you can fill it with solvent, boil it, media blast it, or just about anything else.
The inside can be re-coated with a number of materials commonly used in restorations, and obviously you can do pretty much anything to the exterior. Find a powder coater in your area and ask what they think. Pretty much anything you're going to do will be right up their alley.
I think it's worth repairing them. The whole point of a nice fuel can like that is to buy it once, keep it maintained, and use it as long as possible. If you just toss them, you may as well buy cheap crap.
Cheers,
Kennith