If you've already studied for the MCAT, then you already have a good grasp of chemistry and organic chemistry. Just do problems for those sections. Get Destroyer, your best source for ochem and gchem problems.
For Bio, you will need a good review book since DAT biology is a lot more comprehensive. Get Cliffs AP Bio for the bulk of your studying. Supplement that with Campbells and a good undergraduate anatomy and physiology book. Finally, you will need problems to work. Again, Destroyer is your best source for Bio problems. Know Cliffs AP Bio and Destroyer inside and out....literally everything.
Lastly, you will need practice tests. Get achiever, the best practice test on the market. Topscore is too dated and too easy. Achiever will give you the extra push you need. At the end of it...you should know the Achiever SNS inside and out as well.
That's about it for the sciences, good luck.