It might be helpful to know what front/back combination's are possible and then try to grab those cards that fit your set the best. Here is a link to Trae's website where you can download Scot Readers ebook and Bill Brown's superset,
both are excellent resources that will give you a big jump on the possible front/back combinations.
http://www.t206.org/resources.php
You will find that with several of the cards you will be limited in your quest for a tougher back.
Hope this helps a little
Mike