As I mentioned earlier I did my '74 CB550 gas tank that was in very bad condition through the electrolysis method and it worked incredibly well, and was cheap and easy. The only problem I had was after a few days some rust started showing up again. Have you looked into any methods of lining the tank once you removed the rust? I think I may have to do this. If you have any specific questions about electrolysis let me know I did a ton of research. Make sure you are in a well ventilated area if/when you do it.