Moose, I am not a bonehead! Want a donut?
Ok sir, you have an estate question. When your step father died his debt passed to his estate. In other words everything he owes (to you and others) is now owed by the temporary legal entity created to settle his assets and liabilities called his "Estate." The Executor of that Estate is like the trustee or CEO and the Judge is like the Board of Directors. In other words, you need to make a claim against the estate for the storage fees. If you know the executor and he/she knows of your agreement, this shouldn't be hard. Further, if you have it in writing this won't be hard. If these things are not true then it will be hard.
You make a formal claim to the Executor in writing. If the Executor agrees he/she will pay you or negotiate the car as full payment. The Judge will, on the petition of the Executor and after hearing any objections from your step brother and his "bonehead" attorney, make the decision about putting the title in your name or approving the payment of fees. If none of this is in writing then you can backdoor a contract (30 years is a LONG time to hold a car for free). I think a Judge will agree that you either had a contract, or that you are due
quantum meruit which means the "quantity of merit" or the value of your services.
If there is no "estate" and no "probate judge" involved, there needs to be. Any time a deseased person owns titled property there must be a judge involved to transfer title.