This story involved a young man in the future who travels back to the time of Jesus to meet him only to end up as Jesus. He is able to perform "miracles" because he shares some aspirin from his pocket with a sick person, he is aware of future events, etc.
This story has haunted me for the past 30 years. I cannot seem to find the anthology book that it was in although I purchased the book in paperback form and it was anytime from 1983-1986.
It is not "Let's Go to Gologtha".