Revocable living trusts are virtually always grantor trusts and, as such, are treated as disregarded entities for federal income tax purposes. In other words, the transfers would be treated as having been directly to your grandma (i.e., the fact that a grantor trust held title is not relevant for federal income tax purposes).
As a result, her basis is most likely a carryover basis from 1964 (without knowing all of the precise details, that would be an educated guess).
