Back in the early 70s, there was a fund raising event where people could donate and have a name inscribed on a stone. My grandparents donated in my name. Is there a way to find where this stone might be? They were from Montana if that helps

I think you might be thinking of the Roman catholic national Basilica… The Washington National Cathedral on the other hand, does not have individual stones inscribed with donors names from past fundraisers. There are however, scattered throughout the building, memorial inscriptions on many things, since everything was paid for by donation.

I would check their website for a contact number or email and start there.