You need both Organic I and II to be successful on the DAT. The organic section, in my opinion, is significantly heavier in Organic II than Organic I. Take both courses, then give yourself at least 3 weeks to continue to prepare for the DAT without your Organic coursework to worry about. Do Chad's multiple times. You'll be fine! Also, you don't want to submit your application until your Organic grades are officially on your transcript, as those grades are necessary to calculate your GPA.