Saving a 40 gal gas tank

[matapalo]

I got a hold of a 40 gallon gas tank from someone who's Suburban was involved in a flood. The waters reached over the gas tank filler opening which was not sealed tightly. The tank filled up with flood mud and who knows what else. He pulled it of the burb and left it sitting in the elements for over a year now. My question is, if it is salvageable and how to go about making it useable again?

Here's some pics; anyone recognize what it may have origionally come from? Is it custom?