Thank you all for your input. The Grantor Trust does have an EIN; per regulations "If a trust is a grantor trust, then the grantor is treated as the owner of the assets, the trust is disregarded as a separate tax entity, and all income is taxed to the grantor."

As for the Inventory point, thank you for noting that as it did come up. The parcels donated were part of a larger purchase of land; it was split into 7 lots, 2 to be donated and 5 to be developed for residential construction by whomever buys them.
Fortunately, the FMV from the appraisal is higher than the cost of the 2 parcels, so the land being "Ordinary Income Property" is moot point for calculating the deduction.

So, I will just put the Grantor's SSN on the form. Thanks again!