Strictly speaking, it should be 'If I were he' . Both the 'I' and the 'he' should be in the nominative (or subject) case. However, we have become so accustomed to using object pronouns (me,him,us) at the end of sentences that 'If I were he' sounds wrong to the modern native-speaker ear. Although this is not strictly correct, all native speakers - apart from the most pedantic - would say 'If I were him'. So, yes, I agree with Bre and Tracy - stick with 'If I were him'.

I think I had better give the grammatical explanation for my vote, as follows. "He" the subject pronoun is required because it is the subject complement and not the object. The rule says the pronoun that follows a linking verb is and should be a subject complement, not an object. "Were" is a linking verb (the verb to be in subjunctive mood). That is why we use the subject pronoun "he" and not the object pronoun "him". Jerry should learn this, too.

My vote goes to "If I were he" because it is the only correct answer. It also sounds fine to me when spoken. I would say that the vast majority of my senior colleagues and my friends who are native speakers would use "If I were he." That makes me a pedant by Su.Ki.'s definition. I am fine with that too. Su.Ki. is a "friend" and I am a fan of hers.

You would say, "If I were him." :)

If I were he, I would help you in every possible way. This sentence is grammatically correct. But could it also be written as - If I were he, I would have helped you in every possible way.