About the only way to try, and there are no guarantees, is to keep them soaked in penetrating oil, diesel fuel, etc. Then walk it and hope everything breaks free. The biggest thing determining how easily they free up is how worn the tracks are. The more worn the easier they will free up, but the newer and less worn they are, the worse they will be to get freed up.
Got one customer with an old IH track loader in the same shape. In his case the undercarriage was nearly new when he got it, but it had just sat for quite a few years. What I mentioned above is we did to his and we got about 50% of the tightness out of them within a few weeks. The rest all we can do is hope they free up with use. Good luck.