I turn 64 in December. Can I file for spousal benefits from my deceased ex wife of 18 years? She died 20 years ago so her earnings were minimal. Is what her age would have been a factor? She would have been 61 this September. I am contemplating retirement soon and am trying to not claim on my own until my full retirement age of 66 so any additional income would help

Dan,
Your widower's benefit depends on your wife's earnigs record, not on her age when she died. Social Security can tell you what your widower's benefit is. It will be reduced if you take it before your full retirement age.
Best.
Mike