Like you said, Ochem II an Physics II are very important for the MCAT. If I were you, I would take both classes and least amount of other credits possible(especially with the Kaplan course). I don't know your exact situation, but that's what I would do.
Otherwise, I would take PhysicsII. OChem II is more of a continuation of OChem I, but Physics II is a completely different topic (Mechanics vs Electricity and Magnetism). At least, that's the way it is at my school.
Hope this helps!