In order to determine the sales price of the home from 1985, I would advise that you inquire with the recorder of deeds in your county.
From Ohio Attorney General:
Steps to get a copy of a deed in Ohio
1. Contact the county recorder in the area where the home is located.
2. Request a copy of the deed.
3. Pay any fees associated with the request.
However, typically trusts get a step-up in cost basis at the time of death, so the original cost basis will not impact taxability, and instead you will report the FMV at time of death. Under Code § 1014, except as otherwise provided, the basis of property in the hands of a person acquiring the property from a decedent or to whom the property passed from a decedent shall, if not sold, exchanged, or otherwise disposed of before the decedent’s death by such person, be the fair market value of the property at the date of the decedent’s death.
Importantly, it should be noted that "the assets of an irrevocable grantor trust are not included in grantor's gross estate upon his or her death, those assets do not get a Sec. 1014 basis step-up" (Journal of Accountancy), per Rev. Rul. 2023-2.
Since you haven't shared the type of trust you are filing on behalf of, I recommend confirming this with your trust attorney.
