1. I would still remember the folly of my childhood as if it were yesterday.
Your question: Can I rephrase the above statement into the following sentence ?
2. I still remember the folly of my childhood as if it was yesterday.
This means flouting the grammatical rule, but surprisingly it is often done in modern English. I have the following note from a web-site:
The New York Public Library's Writer's Guide to Style and Usage has this important note on the subjunctive: "The words if, as if, or as though do not always signal the subjunctive mood. If the information in such a clause points out a condition that is or was probable or likely, the verb should be in the indicative mood. The indicative tells the reader that the information in the dependent clause could possibly be true" (155). Cited with permission.
So if you go by this advice, you can rephrase as suggested.
Student or Learner